I have played Mundo for a while now, and i thouht i should make a guide so the rest of you could enjoy him as the incredible solo top champ he can be. This is my first guide, so i don't expect you to think it's perfeckt, but almost ;P
Some of you have probably heard that he can be a great junger, but i have tryed it, and it works, but i prefer him solo top.

For marks I take Greater Mark of Strength simply because I want some ekstra damage in early game, and i found out that it is some og the best you can use, it work at most AD champs, so it is great to have anyway.
For seals, I bring Greater Seal of Resilience which gives you early armor, and this will help you against 90% of top champs. Nearly all top champs deals physical damage or true damage, exept AP teemo. Therefore I also choose Greater Glyph of Warding as my Glyphs to counter the few magic damage solo top, or early ganks from the mid.
So if you wonder why i choose flat magic resist in spite of magic resist per level this is a simple reason, and they don't give you that much more, and anyway your runes are only suposed to help you early game.

For masteries I take 21 points in Defense, and 9 points in attack.
I won't go deep into this, if you use this masteries, you can go where you plases, and deal a lot damage!
It is all showed in the masteries at the top of this guide

I start with riot's recomended items, but not because they recomend them, but they are perfect for Mundo. The Dorans Shield a a startin item will give you more health, armor and healt regen, combined with your passive you will get a total healt regen at 5.9 each second in lvl 1! Mercury's treads will allow you to escape easy. follow enemies. You will also become a much better tank. The spitit visage will increase your healt reagen and you ultimate incredible much, thats why i will recomend this item, it is a mundo item. Then the rest of the itemes will make you more tanky, and mundo got enough damage, so DO NOT BUILD AD!!!!

More healt = more healtregeneration! perfect!
This is you main harass, hand a perfect tankburster! lovely!
This is you only AoE damage, and it reduces the CC on you while active. Combined with you will have 45% reduced tenacity, and you will be almost immune to ganks!
This ability gives you tons of damage! Your basic attacks will deal a lot more damage and it is a turret crusher!
As we all know Mundo's Ultimate is almost OP, and makes you able to stay in lane forever, and turretdive allready at lvl 6. This is my favorite ting aboute mundo, tons of healt regen and movment speed. No, it is not tons of damage, but it is tons of heal!

I take Heal for surviving ganks, get you HP up after using you ulti which will take 20% of you current HP and Ignite for effective killing enemies with lifesteal or a heal, this extra damage will help you take down enemies 1 vs. 1.

You can also bring exhaust for chasing enemies or succsesfull ganks, if not you can bring Cleanse for getting away. If you like Ghost it is a opinion, but you allready got the 35% movment speed form you ulti.

Pros

-Epic Harraser

-Very hard to gank with a CC reduction, if you don't have exhaust and a stun u won't die.

-Easy turret destroyer using

-Great 1v1 champion early-mid game

-Extreme Tanky / really hard to kill or in some cases, immortal

-Nice initiate.

-Goes where he pleases!

Cons

Have in most cases to go solo lane/jungle
Ulti is extreamly affected by healdebufs like ignite.
A meele champion, which makes it difficult to take lasthits.
Don't have a lot CC.

Most teams will enjoy playing with a mundo, he vil be able to slow the enemy every 3.5 second, and he can tank almost everything. If u can make the enemies focus you in a teamfight,they have allready lost the fight. If you wait a while using your ulti and then quick useyou will be able to stay in the fight much loger than other players.