This is my first build, and let me tell you, it is not a quarterback build. It's the offensive guard that I built this for. For all the non-American football fans out there, here's what I mean. Bottom line up front, no penta-kills here. My Alistar build is an Initiator Tank. He charges in to the fight to draw fire, separates the opponent's Carry from the rest, and allows the rest of the team to mop up the mess. As a matter of fact, I average only about 5 or 6 kills per match. BUT (and it's a big but) if the game goes the distance with no surrendering, I usually get 20+ assists per game. So if you want to help your team win more than lead the kill-to-death ratio, this is the guide for you.

Please try this build before you vote, and PLEASE give me comments and feedback. Thanks!!!

2011-06-28: Tried a suggestion from PsiGuard (see comments below). Main build now uses Boots of Mobility instead of Mercury's Treads, however, if you are going up against a Mage heavy team, or if most of their team has stuns/slows/taunts, etc., then I would stick with Mercury's Treads. Thanks to PsiGuard for his suggestions!

Pros:
-One of the best tanks (if not the best) in the game.
-Early stuns with his Pulverize and to a lesser degree Headbutt.
-With a little bit of cooldown reduction (CDR), and some mana regen, you can spam Triumphant Roar. This will keep you and your team in the fight a whole lot longer.
-Ali's Ultimate, Unbreakable Will, can allow you to tank towers, 2v1 situations, some 3v1 situations, and best of all, it will act as a cleanse, clearing all the slows, stuns, etc.

Cons:
-Ali burns through Mana fast, and doesn't have much to begin with. Watch your Mana level, or you will run out at crucial times.
-Range--or the lack thereof. Even your one ranged attack, Headbutt, has a limited distance. So, early on Miss Fortune, Ashe, Caitlyn, etc. will be tough to deal with.
-You're an old heifer, and as anyone who grew up on a farm will tell you, "Them old bulls don't move so fast." I prefer Mercury Treads for their Tenacity boost, but Boots of Swiftness (or Boots of Mobility if you like them more) can make the difference in getting where you're needed.

In this build, Runes help you out the most in the early game. Items are what build the tank you want late game. Hence the majority of the Runes are flat bonuses. The biggest thing that my build needs is Mana Regen. Seals of Replenishment and Clarity are the best at that. Then comes the general Tanky stuff everyone wants; Flat Health Quints, Armor Marks, and Magic Resistance Glyphs round out the build. I do like a little bit of increasing support against Ability Power (AP) killers late game, as well as a little more Mana Regen, hence the three scalable Seals and Glyphs. However, you can go all flat runes across the board, if you want more early game help.

My mastery build is pretty similar to most Tank builds out there. You want a lot of Defense and a little Utility. The important differences are to make sure you get Insight (in utility) and that you max out the Ardor (Defense). Your lane partner (and later the whole team) will benefit from your Clarity Spell with Insight. Ardor adds Ability Power (AP) and Attack Speed (AS), two things that add to your damage output. The AS isn't super important, but the AP will help you get the most bang for your Pulverizes, Headbutts, and Triumphant Roars.

My Top Choices:
Clarity: For you to get the most out of this build, you want Mana Regen. Clarity gives you the ability to stay in the lane longer early game, and (with Insight) will help out the whole team late game.
Ghost: This is my personal preference for faster movement. I've tried teleport and flash, and both have their own merits. I prefer Ghost because no matter where you are on the field, or where you're trying to go, it'll get you there. Combine it with your Unbreakable Will to get out of a bad situation. Or combine it with Headbutt (and/or Pulverize) to initiate a fight.

Other Options:
Flash: Good for short hops into or out of situations, but not as helpful when you're crossing the map.
Teleport: Good for crossing large sections of the map. The only problem is if there's a team fight in the jungle, or you want to go somewhere with no one you can teleport to?
Clairvoyance: It's not a bad idea if you team it up with Teleport to defend the whole map.
Fortify: Great for defense. If timed right, you could Headbutt or Pulverize your opponent and then trigger it to do a lot of damage. However, it's not much use once you start "tipping" their turrets over.
Exhaust: It adds another trick to slow/stun your opponent, but Pulverize and Headbutt normally are all I need.
Ignite: If you want to be a little more aggro, then go for it.

Don't Get These:
Heal: Triumphant Roar does it for you.
Cleanse: Unless you're just slamming into every team gank you can find without any backup, Unbreakable Will covers this.
Smite: This is not a Jungling build, although Ali can do that.
Rally: Not once have I seen someone use this skill, so I can't really say--but I think not.
Revive: The only Champion I have seen who uses this much is Kog Maw. Otherwise, if you take this, expect derision and many noob accusations.

All of the old Bull's skills are useful, however you use Pulverize and Triumphant Roar most often. Headbutt is useful to initiate contact, so do get at least one rank. Try to focus on pushing your opponents into your teammates or turrets with an early Headbutt. Then, let your partner smash 'em up--and when they try to run away, Pulverize them. Get Unbreakable Will whenever it's available. It's a force multiplier if you time it right, both offensively and defensively.

I listed the items in my build up top in the order that I generally buy them, here's my explanation why.

Starting out:

I like to start out with this combo, in getting ready forSheen. With Sheen, spamming your Triumphant Roar allows you to farm a little better and bash your opponents twice as effectively. Next it's time to address your slowness and your money needs.

Early Game:

These three items should make you harder to kill, get your money flowing, and allow you to keep up with your laning partner better. Soon after the Philosopher's Stone, I getKindlegem for it's CDR and extra health, thenThornmail for it's armor and to make attacking you less appealing.

Mid Game:

The Boots of Mobility upgrade, and the Thornmail can be bought in reverse order depending on if you need faster movement or Armor first. In most cases the Armor and extra damage makes the Thornmail more useful, but swap it out if the boots fit better at the time. I then upgrade the Kindlegem intoSpirit Visage, giving you better Health, Health Regen, Magic Resistance, and CDR.

By this point in the game, you're roaming from team fight to team fight, so theAegis of the Legion is the next pick-up.

End-Game:
Most of the time, my team has already won at this point. But in longer games, your Sheen should update to a Trinity Force. Then, upgrade the Philosopher's Stone into a Shurelya's Reverie. A lot of people likeLich Bane instead of Trinity Force. However, it isn't really as useful, as double your base damage is a lot more than your AP.Eleisa's Miracle is another viable option to the Reverie. I find being able to speed up your team on a chase is more useful than the Tenacity. Again, make your decisions according to your opponents.

Now we're finally to the general play-style of this build. Your lane partner should have a higher Damage Per Second (DPS), but you want someone who won't go super aggro. Take it slow, and once you get Triumphant Roar, start to push the lane. You should be able to stay out long enough with one health potion and the Roar for you to use Clarity twice. Then go back to get your Sheen (and the boots if you can afford it). Use the bushes (especially the river bushes) to set up your Headbutt, knocking them to your team mate. Remember, you're there to support the whole team, so look for opportunities to help gank in the other lanes. Headbutt can also be used to break up a gank on a teammate. Target the biggest DPS source, then follow up with Pulverize to stun the rest. Unbreakable Will needs to be timed so that slows, taunts, stuns, etc. will be cleared off by it. Be careful though, if you wait too long you won't have enough life to get all the way away.

"Cow-tipping" is a really ridiculous thing that country kids sometimes do. If you're not familiar with farmyard animal traits, you should know that cows sleep standing up. So when rednecks get REALLY drunk late at night, they'll go out to the pasture, and run full tilt into the cow to tip it over. Heaven help you, though, if you try it on a bull. Turrets can be "tipped" in much the same way, leading in with Unbreakable Will, and spamming Triumphant Roar to get back your health and activate Sheen (or Trinity Force). You can also activate the item with Pulverize every time the minions get around you to up your damage.

Remember your passive, Colossal Strength, triggers off of every skill. So time it right, and you can trample for quite a while. It's a good way to increase your farming ability.

Well, that's it, now go out and TRAMPLE somebody!

Please vote and comment! Thanks!