Dr. Mundo Build
Not Updated For Current Season
This is how I play Mundo. This build lets you stay in lanes forever, be a meat shield for your team that never dies, and a good tower pusher.
Starting off with a Doran's Shieldis very common on a Mundo build. The added armor, health, and life regen are pretty much all Mundo ever needs. The health pot is also good for some extra quick health regen if you are in a lane with a lot of harass (Even though you should be doing most of the harassing). You should try to stay in the lane until you have about 1700 gold.
On your first trip back try to buy the Spirit Visageand Boots of Speed. If you can, go straight for the Mercury Treads, unless their team has absolutely no CC, which is very unlikely.
On your second trip back, try to build up to either a Randuin's Omen, or a Force of Naturedepending on the enemy teams composition. I usually build a Force of Nature first unless they have 3 heavy DPS. The force of Nature gives you great health regen and movement speed, which helps you catch up to runners and cleave them in the back.
Most of my games have ended before I could get to the next item, but if you're in a drawn out game you should probably go for either a Warmongs, a Banshee's Veil, Guardian Angel, or a Thornmail.
Warmongsis good if they don't have too many nukes because it lets you slowly gain back your Hp while they try to get it down.
Banshee Veilwill rarely be needed, but if the casters are hurting you too much then get it.
Guardian Angelis good to get some more armor and Magic resist, but the passive should never have to kick in.
Thornmailhelps against Twitch, Master Yi, and Kog'maw. They usually end up doing more damage to themselves than to you.
The reason I get Magic Penetration Marks is because they help your cleaver hit harder. This can usually be used to get early kills or forced recalls on enemy champions.
The Health per level seals are great because they increase The health regen you get from your passive and Ult. The reason I choose these ones over flat is because you should start the game with about 860 health, which is more than enough.
Magic Resist glyphs because they are always useful. (You can substitute CD reduction for these if you want).
I try not to get my Burning Agony until I have to. Merc treads should give you all the CC reduction you need.
Ghost and Teleport
Ghost works well with your ult and helps chase down runners or helps you get away.
Teleport lets you get back to lane faster and just helps you be where your team needs you.
This build wont get you to many kills, but it makes you a team player and a great off-tank. Taking a side line with another character with good harass should ensure you complete lane control.