This is my very first guide, so stop reading now and proceed with downvoting me and leaving negative comments. A little about myself: I have been playing League of Legends for quite some time now. The champions I am proficient in and enjoy the most are Mundo, Singed, Pantheon, and Teemo. I am not going to post screenshots of my history to prove to you this guide works. I will let you test the guide yourself.

I see many builds that have Mundo stacking health, armor, items used to soak up damage. I laugh at these builds because I know that I only need to dedicate half my build to survivability, build the rest into damage, and substitute the lost survivability with my own common sense.

I am not sure what is up with these AP builds I have been seeing lately. I was frightened to see an enemy Mundo jungle with Clairvoyance and made getting blue buff his priority. Needless to say he didn't do so well.

A lot of people tell me Mundo is a tank. Generally tanks are champions who stun, taunt, etc. Seeing as Mundo doesn't do any of that, I am less inclined to call him a tank. Call him what you want, but Mundo (if built right) is a champion who can take damage, and deal it as well.

I don't worry about runes too much. I am not very pro and end up using the wrong rune page most of the time, and still do good. When I am using the right rune page I am using health, magic resist, and armor pen. Again, it won't be the end of the word if you don't use these exact runes, especially if you are below level 20.

Mundo is a tricky champion to build a mastery tree for. Nearly all the bottom masteries don't help Mundo as much as I would like them to. Because of this I dip a little in all trees, getting what actually can be used by Mundo. The first things I always pick are improved ghost and exhaust.

If you jungle, get greed, and obviously skip whichever mastery spell you dropped for Smite.

I see a lot of people build Mundo as an all out tank, then they get no kills, but a lot of assists, and their defense is "well Mundo is a tank, not a DPS." I build Mundo as a DPS with the required defense to survive. I tend to be the one getting all the kills.

People always tell me to get Warmog's Armor first, but I usually wait until late game to get this. Most people's reasoning behind getting Warmog's first is because it takes time to max out the stacks. Seriously, it doesn't take long to max it out, especially with Heart Zapper.

Start off with Doran's Shield. With the changes to the price of that item you can no longer get a Health Potion with it. You don't need it anyway. The armor and health on Doran's Shield is nice, and gives you survivability to farm early in the game. Don't be an idiot, have map awareness, and you won't die early game.

My second item is Emblem of Valour, if you are laning by yourself, or laning mid (yes, Mundo can lane Mid) then skip it for now, and get this item when you would have normally bought Zeke's Harbinger. I don't need to tell you that having this item will help out your lanemate as well.

Ionian Boots of Lucidity - This paired with Spirit Visage will allow you to keep Masochism up all the time. Early game these boots are very nice. Late game you want to drop them, and get Mercury Treads.

Heart of Gold and Avarice Blade - The extra gold will help out a lot. Heart of Gold will help with survivability (obviously) and Avarice Blade will help with farming (obviously). Heart of Gold can be upgraded into an Randuin's Omen late game, or sold for another item.

Spirit Visage - Get it. Just do it. No questions.

Zeke's Harbinger - Everything on this item is great for not only you, but the team. There is no "I" in team. Get this item, win the game.

Warmog's Armor - Great item. Paired with Atma's Impaler, it can be a deadly item.

Youmuu's Ghostblade - Another great item. A late game must.

Situational:

Randuin's Omen - You can sell Heart of Gold and get an item that better suits your needs or keep this item.

Atma's Impaler - This will let you tank towers a little better. An excellent item if you are torn between the other two situational.

Force of Nature - Only get this if the team is heavy on magic, otherwise it isn't that useful.

"Why you no get at least one rank of Heart Zapper in early game?"

Because it sucks early game. It drains health way too much health, it doesn't do much damage, and it just isn't great early game. I wait until late game to get the first rank of it. Activating it early game is a death sentence. Wait until late game when you get more health regen.

Everything else is self explanatory. Do I really need to write a well written section on why Maximum Dosage comes first, Infected Bonesaw comes second, and Masochism comes third?

Goes Where He Pleases - More health, more HP5. 66 HP = 1 HP/5.

Infected Bonesaw - Great for harrassment of minions and champions. Use it to last hit minions, kill steal champs, check bushes, or throw past walls. Those epic last hits on champions behind a wall will make you VERY happy. Since it has no mana cost, it is spammable. What makes you better than Pantheon, Urgot, or any other champion with a similar ability is that you will always be able to throw your cleaver. And if you can't afford the health cost you should probably not be in the lane anymore.

Heart Zapper - Great spell late game. Reduces CC and damages everyone around you. Also great for when one of your towers is getting smashed by a large group of minions. Pop on Burning Agony, run in, and enjoy the gold.

Masochism - Always use before you throw a clever at an enemy champ. Use it if you think it will kill the minion when it otherwise wouldn't. Late game you should have enough CDR to be able to have this spell on all the time.

Maximum Dosage - If you are at around 60% health, regardless if you are in a fight, use it. The cooldown is short enough to allow you to use it out of combat. Use it to chase, if needed. Tower diving with this spell becomes possible later in the game.

Ghost and Exhaust

These are really personal preference, I like ghost for quick escapes. Ghost plus ult will make you run through most CCs. Exhaust and ghost are great for getting first blood and that nice gold bonus before the minions even come out.

Heal - You don't really need it. Your ult will keep you properly healed, and with its short cooldown, it is spammable. You shouldn't need the health in a pinch that this spell offers.

Revive - Getting this spell means you expect to die. If you expect to die, thats alright, just don't expect to win.

Smite - Jungling Mundo could work. Get this if you choose to jungle, more information about jungling is in my jungling section. Smite can be paired with either Ghost or Exhaust.

Teleport - Not that amazing. Skip it.

Cleanse - A possibility, not the best choice, but better than revive.

Fortify - Let someone else take this ability.

Clarity - One of the best spells for Mundo to get. I would highly recommend this for any Mundo build. A real must.

Ignite - Not that amazing. Skip it.

Rally - Not that amazing. Skip it.

Clairvoyance - Let someone else take this ability.

Flash - Flash can easily replace ghost. It is a personal preference, I prefer ghost, you may prefer flash.

It is possible for Mundo to jungle. If you do choose to jungle, get Masochism first. Make your first item Vampiric Scepter and build into Emblem of Valour. Once you have your ult and Emblem of Valour you can solo dragon. Run in, pop your ult, and spam cleavers. You do not have to be jungling to solo dragon. This is why I prefer bottom lane as Mundo.

Don't intiate. Keep Burning Agony up. Keep Masochism up. Target the carry, attempt to throw cleavers, although if there is a cluster of enemies, it can be difficult to land one. Chase down the stragglers and runners. If you start taking damage, pop your ult, don't save it. If you are about to die, run out and wait for you ult to bring you back to full.