Please if you vote -1, ground it in with comment so I can reconsider some choices if needed. If you vote +1 (which I assume) but have some other ideas, let me know as well!!
But always try few times before voting!!

This is the first build I created and think this is the way to play mundo. It will give you great survivability, a lot of assists and kills, and the most important thing; it will make you a great killing tank for your team.

I'll write three scenarios for playing Mundo. I think there shouldn't be a big difference in builds for 3v3 and 5v5 (Mundo is kind of OP in 3v3 ^.^), but it's important to have different builds dependent on your enemies team. So I'll write a build for a game against an AD, AP and mixed enemy team.
I won't make it a long build; I'll only include the things that are necessary to know. The basic of those 3 scenarios is to play a great healthy Mundo.

The builds are the same in the starting items. It depends on a game which build to use. Even if the other team has got mixed characters, it's not always necessary to use the 'mixed' build. It's dependent on which enemies are becoming a danger and which enemies aren't that good to buy resistance or armor against. But that's something you have to experience yourself.

Infected Cleaver - This is an ability you might use the entire time. With the it's easy to use a lot in early game as well and it does a lot of damage. It's also great to annoy and harass enemy champs.
You can also use it to last hit minions and you can explore bushes.


Burning Agony - Especially in mid game you'll use this ability to farm very easily. Later you'll use it to hurt all the champions that are around you and more important; to reduce the time of negative spells casted on Mundo!

Masochism - This ability can be used if you need to kill minions faster and with a hand to hand fight with another champion. You hit a lot harder while using this ability.

Sadism - This really is a great ability, especially if you have a lot of max health. You can use to stay longer in lane, to stay alive in teamfights and to flee (bc of the health regen and movement speed) when farming a lane on your own.

Adrenaline Rush - Dr. Mundo regenerates 0.3% of his max health each second. Works great with the entire health build.

At first it's important to choose your Spells well. I think Exhaust and Ignite are the best spells for Mundo to use. This for an easy fb, especially in 3v3 and you don't need ghost or flash because of the movement speed you get from your ulti.

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Because of Mundo's ulti and the fact that his skills cost health, I choose for health runes and a little extra magic resistance. With this Runes and the item-build it is quite easy to stay in lane for a long time.

The masteries aren't hard to understand. I think it's important for Mundo to have great defense and a great Cooldown Reduction, because especially your and your are very useful! Also your will take advantage of it.

Also take notice of the 15% penetration you get from your masteries!

One important thing for choosing the item build; choose your build against their 2 or 3 strongest champs. If the got 2 strong AP chars, one strong hybrid and a weaker AD, don't choose the mixed build, but the AP build

The most important thing is that the build will become 'yours' so I give some item alternatives.



Now we are at the item part, which is the point where you might need the most help, because it's difficult to choose the right items of all those possibilities. This first item build is for a game against a mixed team.

Those games are the games that are tough to play.
For Mundo health and health regen are the most important things to get (asap). This will increase your survivability, your is better and you can farm better because you can use more often.

So I always choose to start building . The first items to get is . This will increase your time you can stay in lane, also with the health regen you got. When you reached level 6 it's only easier to stay in lane and farm more with .

If you don't have enough money to finish when you have to go back to base or if you need movement speed, you should buy first.

During the game you will experience farming is easy and your health regen is becoming quite good. Finish your and your (which is great with your for reducing the duration of negative spells) and farm asap to fill your warmogs.

To get some more health and Cooldown Reduction, it's time to buy a . This will increase your health and you can use your Cleaver and Sadism more often. Besides that, your health regen will be increased again.

Now it's up to you which items to take after you have the standard first 3 items. Because the other team is mixed you need to consider what you need first; if their AD chars are the best or you come in fight most of the time you might need (rec bc of health) or first. If not (so AP and AD got the same strength or AP are the best) I prefer first. This because of the Healh regen passive. Afer this you should get the or . I always play with or but you can also choose for , which is more expensive but has a great active and got health and regen.

The last item is in this kind of games a free item. Most of the time it's useful to get .
But there are alternatives:
Because Mundo does a lot of Magic Damage (have a look after the game) I sometimes choose , which gives more AP, slows and gives health. But if I'm getting sick of the AP chars I choose for magic resistance, AP and the negative spellblock once in everey 45 seconds. If I get sick of the AD chars, I try to build .

At this stage of the game you're indestructible if you use your well and you can use your the entire time for 'free'. This build will give you a lot of kills in teamfights and a lot of assists. Chasing enemies is easy as well.

If you read the Mixed Team build, this build doesn't need any explanation anymore.

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This doesnt occur that often and this is a build I dont have tested a lot. This build will give you a lot of Armor, but you might consider to replace one of the three items with armor for a health and magic penetration/AP item you might like.

Pros:

Great farmer.
Great lane pusher with escaping abilities.
Very hard to kill.
Can slow during chasing.
Last hitter with Cleaver (dont 'steal' too much, some allies need stacks!)
Relatively short cooldown reduction for abilities.
Good solo laner (with/under turret).


Cons:
Little squishy early game, don't use burning agony too often!
Hard to time sadism (especially with stunners and silencers against you)
Not a real tank.
Need practice for the cleaver, looks easy, but it isn't.

If you got a Jungler, you are pretty good to hold lane on your own with your health regen, your cleaver and your burning agony. But you should be careful; you are kind of squishy early game. But if you reach level 6, you can push a little and harass the opponents some more. Besides that, use your burning agony to farm a lot and get a lot of money (and with that health) early game.

If you are with another champ early game (until lvl 6) you can be very annoying and harass your enemy with your cleaver (even under their turret). Try to use your burning agony when minions are low health, but be careful with your health; you are a little squishy early game.

If you survive well you can start farming from lvl 6. When you have enough money to build Warmog's armor try to stack it up to maximum asap. Use your burning agony to do that. If there are little ganks going on in which you're not needed yet, you can easily and quickly push lanes on your own with burning agony If the enemies are coming your way and try to gank you, you can get away easily (even against 4) with your ult, Ghost, the cleaver and burning agony.

Late game you are the one to initiate the ganks, you do great damage and have got a lot of health; make sure you use all your abilities and use your cleaver (slow) for last hits and for enemy champs that try to get away. With a good team behind you there's now way you can lose your ganks, because you do a lot of damage as well.

At last, enjoy the sound and feeling of another victory.