Kayle has second highest base HP in the game, so why not actually use it to your profit? She also has a very long ranged heal, slow and a ulti that's specifically suited for a support character, therefore she's very capable of saving lives. That's why I like tanky-support build. Core build is affordable due to gold per 5 items and very often you can see Kayle's with almost zero damage even if they seem to have a nice damage based build. I like hybrid Kayle, but it seems nowadays playing her hybrid isn't as viable as it used to be, but now she's a better support than she used to be.

Kayle used to have a slightly boring early game and low damage until late game unless you farmed like hell. Nowadays she has stronger early game even without items, which you'll be using to your advantage as a support.
As a support Kayle can have a high damage depending on if you continued to be a full support or began getting some items best suited for Kayle, like Nashor's Tooth. That's why her late game as a support differs from other supports in the way, that should be more appreciated since:

• compared to other supports her damage can be superior especially late game
• her heal range is far longer than other supports allowing her to save from distance
• transition from support to a carry isn't as expensive or inefficient as with others (check the Game Stats section for details)
• building damage items on a support is actually useful to your team, when you can have 5 carries instead of just 4 without losing any supporting capabilities
• Kayle is durable throughout the game compared to squishy tier 1 supports like Sona and Soraka so she can initiate without dying in an instant
• her ulti allows hard core turret diving when playing with skilled people

Pros

+long survivability
+high defenses
+slow & speed buff
+longest heal range (exluding Soraka's ulti)
+cheap core item build
+can save an ally with her ulti or help with initiation by using it
+decent damage early game and late game, even if mid game is a bit blunt
+aoe damage on a support

Cons

-low damage mid game
-no AP for better heal
-low ap ratio on heal for that matter...
-prejudices of other players when played as support
-better farmed than not farmed
-long cooldowns early game

• Hybrid penetration runes for extra harass power with both auto attacks and spells.
• Armor seals for better defenses + works well with Defense masteries.
• Extra magic resist from glyphs doesn't hurt.
• Gold from quints.

• Summoner's Wrath for better Exhaust.
• HP from Durability , Veteran's Scars and Juggernaut
• Armor and magic resist from Hardiness , Resistance and Legendary Armor
• Extra tenacity from Tenacious is always good
• Honor Guard isn't a must, but it's still great with the rest of the masteries and the build as it reduces damage taken by 3%
• From the Utility tree I take reduced flash cooldown from Summoner's Insight and some mana regen from Meditation
• Shorter summoner spell cooldowns with Mastermind

Note: Usually on a support I invest into Utility tree to get extra gold income, but with Kayle and Leona I prefer to play tanky so I invest 21-22 points into Defense tree instead to get all the lovely defense bonuses. Since this is a Tank Support Kayle, the masteries fit better than investing hardcore into Utility.
Another setup for Kayle is going 15-15 into Defense/Utility and getting the gold income masteries.

Good for escaping purposes. More like a must-have summoner spell.
Nowadays your carry is the one picking heal so you're left with having the CC spell Exhaust, which works rather well with Kayle actually.
This must be the most popular summoner spell nowadays and also good for a support Kayle since your own heal isn't as good as Soraka's or Sona's heal.
For supporting purposes if you feel like having extra map awareness.
You can pick Ignite as a support Kayle, but it makes killstealing rather easy. However if you plan on being early game support, late game carry, this is a good spell and it shuts down healers like Soraka or lifestealers like Vladimir.

Skilling Order for a Support Kayle:

Righteous Fury for ranged attacks simply and maxed after heal to increase your damage, since Reckoning is better used for slowing enemies, but this will increase your damage for multiple enemies rather than for just one.
Divine Blessing maxed out first for maximum heal power and support to the team.
Reckoning is a choice to max out second, because it increases the slow amount, but can be maxed last if you prefer aoe damage. Early laning it's better to have higher slow amount than damage considering you want to give kills to your carry. Double-edged sword...

Kayle's passive skill is Holy Fervor which will shred the defenses of enemies percentually, which makes this skill rather useless. However building some attack speed will allow you to fast reduce the armor and magic resist of enemies by 15%, which is calculated before magic penetration/armor penetration, so it actually helps a bit.

Your main disable skill is Reckoning, which can be maxed second for epic slows or last if you prefer aoe damage. However as a support you might wanna invest into maxing this second for the slows since mid game your team will do enough dmg for you just to concentrate on slowing enemies.

• Reckoning is a great skill for initiate on both early game (like Taric's stun) and late game when you're tanky enough to initiate
• You can use this spell to save your allies, by slowing the one chasing your carry for example and starting to hit them
• Can be used for harassing together with Righteous Fury
• If you built AP you could use this for burst damage

Kayle's heal has probably the best single heal range in game even after the recent nerf. While laning early game and sitting in bush, you can heal your ADC who is almost by the river. Divine Blessing has a 100 heal power at lvl2 so it's a relatively good heal even at low levels. It can be used for healing and helping your allies run as well as chasing by using it to the chaser to give them greater movement speed. By timing your heals well, Divine Blessing can be truly worth picking Kayle to your team.

• Using Intervention first and then using Divine Blessing will allow your badly positioned ally to run to safety
• Combined with Reckoning you can either escape from an enemy or ensure that they won't be getting away from you and your teammates
• Outranges Astral Blessing and Hymn of Valor as well as Imbue
• Works especially well with fast characters like Vayne
• Decent heal power at max level and with proper CDR can be used often

As a support Kayle damage isn't your main focus, but as Kayle you're capable of doing damage more than other supports if you max Righteous Fury. Difference to other supports is that you can do continuous aoe damage with this spell rather than using auto attacks or single targets spells every 7 seconds. This spell will give you epic harass power early game and nice damage throughout the game during teamfights so you never have to be passive, but you might want to max this after Reckoning if you need CC more than continous damage.

• Early game it's easy to zone the enemy by using Reckoning and then hitting with Righteous Fury on to keep them at bay, since you're durable enough to take some hits
• Extra damage from Righteous Fury is always useful during teamfights and you can shred the enemy defenses with your passive (and items) when this spell is on
• Even as a support pushing has never been this easy, since you can clear a minion wave with Righteous Fury quite easily when this spell is at higher levels

Intervention will grant short immunity to the one you cast in on. Mainly you should use it to save the ally with least hp and sometimes to prolong the damage your teammates are able to do by casting it early, with some exceptions:

• Don't use it on your tank, because if he dies it's better than your carries getting killed, unless he is diving and your carries are all safe
• Don't use it on yourself either unless you're the last one alive
• Stay close to your carry in case they get focused and will need this.
• Sometimes it's a good thing to use ulti on the teammate that has by accident positioned themselves in the middle of your enemies, to allow him/her to run to safer position
• Can be used before someone is about to die, for example Fiddlesticks or Kennen running in the middle of all enemies while their ulti is on are best targets to allow them to deal as much damage as possible
• Can be used to turret dive, but only if you are sure either you or your ally will get a kill

Sometimes teammates seem to play a bit reckless when you pick a Kayle, because of your ulti, but you must let them know that they should play like they usually do. They're not reckless with Soraka either, so why they should be with you? Intervention can save an ally, but unlike Zilean's ulti, it's not for granted.

With Kayle I start out with Faerie Charm and Wards. No potions because she doesn't need them.
If you have Wealth mastery you may start with the lower one.

Boots:

Merc treads are always a good choice for the extra magic resist and Tenacity.
For the cooldown reduction.
Against heavy AD teams.
Fast warding and roaming.

Tanky support items:

Basic affordable support item you should buy in every game unless someone else buys it.
Upgraded version of Aegis of the Legion with a shield active. Even if the jungler buys Locket of the Iron Solari it's still a good item to get.
Usually your jungler or top laner buys Randuin's Omen, but nothing else than limited gold stops you from buying this. The active slow/attack speed debuff helps everyone in your team.
If you bought Warden's Mail, but didn't want to buy Randuin's Omen after all, Frozen Heart is a good choice since most junglers and top laners DON'T buy it even though it's very useful against AD heavy teams. *readers choice*

Additional Items:

Shurelya's Battlesong helps you initiating or escaping with the active and gives you nice HP/mana regen. I'd get this in late game so your Philosopher's Stone has time to stack more gold.
Zeke's Herald Zeke's Herald is more offensive support item that works for teams with plenty of AD characters. It benefits both them and you as Kayle by proving AD, lifesteal, CDR and HP.
Usable against heavy magic user team, provides 20% cdr, lots of HP and a very nice magic resist for an affordable price. Does not provide anything for team, but you heal yourself better.
Expensive, but usable since Reckoning has a relatively short cooldown. Provides 10% cooldown reduction, some armor and a slow after every spell use. I admit some other supports like Taric and Leona benefit more from this, but it's usable on Kayle.
Usable for initiating or scouting whether or not the enemy is taking baron or not while you're going there to ward. No more facechecking when Twin Shadows active is off cooldown.
Usable with melee initiators who jump in the middle of many enemies, like Jarvan IV or Amumu, Malphite etc... Also built from Kage's Lucky Pick which you may buy if you want to be less tanky and more... offensive/CC based.

-Don't lane with another melee preferably: you'll get raped
-Early game your mana regen is nonexistent, therefore use it mainly for heal and slow if you're ganking someone
-Roaming can be a good choice if your lane partner is doing well alone
-Build up Philosopher's Stone as fast as possible for more coins, because you shouldn't be farming too much - delay upgrading it
-Mid to late game you should be quite sturdy, therefore allowing you to distract your enemies whereas your teammates can kill them in teamfights
-Late game be a shadow to your carry, go ward dragon and Baron, CV bushes, buy an Oracle's Elixir with spare money and go to destroy their wards
-Use your tankish nature to your advantage and position yourself between your carries and the enemies to take most of the damage yourself while your carries kill them
-Stay close enough to allies to heal them when needed, your heal range is quite long, but you might wanna do damage to your enemies as well
-Since Kayle's heal has a speed buff and you have your slow, you should be quite the escape artist
-Use slow from Randuin's Omen in addition to your own
-Use speed buff from Shurelya's Battlesong in addition to your own speed buff, for chase and escape
-Take advantage of other actives like Locket of the Iron Solari so it shields all your allies
-Don't ulti yourself unless you're the last one alive: you should survive quite a bit of punishment
-Tank turrets, not enemies 1v5.

Here are scores and stats from a couple of games with this build.

These are old as hell taken around S1, but I'll keep them here anyway to point out how long this build has worked for me.

Kayle is a very underrated and underestimated champion even though there are many different ways to play her, suited for multiple situations. People dislike her because they've never either seen a good Kayle or can't play her themselves.

I created this build to demonstrate there is a completely different way to play Kayle, other than all those hybrid Kayles with recommended items who pretend to be original. It's ok to play her like that, obviously how she was meant to be played. This build is to offer an alternative for those who are sick and tired of seeing Kayle as a ****ty champion. She can be so much better than her label gives her credit for.

Thank you for reading and voting on my guide: please let me know if I have missed something or be free to just critisize my choices. Opinions on my guide are very much appreciated as I will keep on updating the guide.

2013/4/29
- Edited the Build itself, added item options, made an Items list and Build variables. General upgrade to the guide, I'm sorry I didn't do it earlier and let the guide be expired for so long. :)

2012/12/29
- Edited the item build and masteries since they were really outdated. Sorry that it took me so long, but I've been busy with other stuff and my Soraka and Sona builds have been my first priority here on Mobafire. But now the guide is updated and usable :) thanks for waiting everyone.

2012/7/27
- Edited runes and masteries, deleted the tanky support build to have only the offensive tanky support build that I use more than the old build (maybe I changed the original too much so I didn't use it anymore <.<)
- The old build is still in the guide regardless, you can still read about it in the Item build: Tanky support section.
- Edited the Offensive Support section
- Rewrote runes section and edited Summoner Spells, Masteries and other minor changes to other sections of the guide

2012/4/19
- Added a small notification of the latest patch concerning Kayle, it won't effect the build in anyway however. Will probably update the guide further a bit later, been busy at work recently (= not busy, I'm at work atm, but I'm just lazy.)

2012/2/10
- Added the new support items Locket of the Iron Solari and Zeke's Herald into the build. I love Zeke's Herald on Kayle <3

2011/12/31
- Yes I'm doing something like this on a New Year's Eve, but I'm waiting for my bf to go to sauna with me so I don't have anything else to do...
- About the guide actually, I've rewritten the item section and divided it into two separate sections for both builds and yeah, I did this on several days before publishing
- Also made Starter & Core Items section, so that makes actually 3 item sections
- Separated Skill Tips section from Skill Sequence and edited both, basically wrote more about every skill
- Added a picture about a recent game with Offensive Support Kayle
- Happy New Year!

2011/12/28
- It seems I'm editing this guide always 28th of the month :D Lol, but I meant to say I did rewrite my masteries section completely, added heal to Summoner Spells and removed Teleport
- Edited Runes section and added the new magic pen/armor pen runes, which obviously don't work yet here on Mobafire, but that ain't my problem :3 I just hope they fix them.
- Removed Reworked Kayle section as it's no more reworked, she just is.. Kayle

Oncoming: rework on the Items section (not the items, just the look, it looks dull now so when I have time I'll make it look better)

2011/10/28
-Added picture from the second build game

2011/9/28
-Added pictures from masteries and skill sequences to go with the guide
-Edited both item builds to be more affordable and better suited for current Kayle
-Edited Masteries and Item Build sections

2011/7/28
-Added a new alternative support Kayle build with new items due to Kayle rework
-changed Item Build section
-added Rework Kayle section
-edited introduction and Runes

2011/7/24
-Edited Item order and Item build section to match the build and make the most of support Kayle