I love playing Rumble. He's an excellent harasser and is really fun to play, when your enemies run away from your Flamespitter, which you can spam nearly all the time. People say, that he is OP. I disagree. Champions like Renekton can handle him with no problems, I tried it. If you know how to play against Rumble, you will find out that he is NOT OP!This is my first build and I'm not english, so I hope that I'll say at least sth good in here.

Mark of Magic Penetration - these are good for all AP champions. I suggest them. Glyph of Evasion - due to Rumble is sort of AP tank, he needs some defense. I like these because of Nimbleness movement speed boost. Glyph of Ability Power - you may replace these with Glyph of Scaling Ability Power, but I preffer those, because at lvl 18, you'll have AP items and Glyph of Ability Power are good in early game, where Rumble dominates (he dominates whole game, but who cares :)) Quintessence of Ability Power - same reason as the Glyphs.

Pros

- very good harrasser
- very funny
- long range ulti with a lot of damage
- low cooldowns
- nice emotes
- probably best chaser in game
- very strong against squishies

Cons

- vulnerable to jumpers like Renekton ( Slice and Dice)
- hated by those who don't have Rumble
- The Equalizer is hard to put first few games

Mejai's Soulseater if you are not a n00b, you will get stacks, at least from assists. Otherwise start with Doran's Shield and build Zhonya's Hourglass after Rabadon's.. Mercury Treads - dodge boots have been changed from the Sejuani patch, so now take the tenacity boots instead. Situational item is the mpen shoe.
Rylai's Crystal Scepter is choice no. 1 for Rumble. With this, you slow your enemies with Flamespitter + slow from Electro-Harpoon to kill your enemies faster than they would make a step Rabadon's Deathcap - AP item to deal some ultra-awesome damage Abyssal Mask - I like this tanky AP item because it grants you Magic Resist + reduces your enemies magic resist! Lich Bane - Even though this grants mana, its a small amount and I wouldn't care. After whole build, with Lich Bane, you deal 400 per hit!

Skill sequence depends on situation, but I generally use

W>Q>R>E>E>Q

Rumble is excellent in team fights, because of The Equalizer!
Simply, if there's a lot of enemies fighting near your allies, throw it there and enjoy your kills!!! Don't forget that The Equalizer has a huge range and the range is used only for the beginning of Equalizer.
The Equalizer is really hard to use 1st or 2nd game.. Your mouse can go wild and I've seen lots of Rumbles that were throwing The Equalizer in the bush because they were just unable to put it where they wanted it.

Laning

Rumble is a solo top champion. If you are going bot, Try getting someone like Blitzcrank with you on lane. Then you can easily slow them and finish them off with Flamespitter. If there are more tanky champs on your lane, I recommend a switch to the more squishier side, because Flamespitter really owns squishies!But Blitzcrankis for everyone huh?OK, let's talk about some champs that are very effective with you. Soraka - she may heal but you don't need her mana present so rather take Kayle or Sona.You want some kills with your mate?? Nocturne - Slightly OP damage some say and fear. Hell yes! Tryndamere - If he's good, and he's got runes, he has to do really huge damage + huge slow from Mocking Shout Xin Zhao - Audacious Charge, throws up with Three-Talon Strike and all this time you can burn the ***es of those squishy Teemo and Vayne.This was the short list of melee champs. You may also try Warwick, Master Yi and Gragas can work out very well.Ranged? Not very effective with you in my opinion. If yes, then it would be someone like Ashe(GOD, don't let her mid), Vayne, Teemo].Tanks! Why not?[[Amumu is no. 1 choice for everyone. Bandage Toss can lead to a nice surprise ending the life of one annoying champion. Maokai - this is really funny champ, harrassing with Sapling Toss. Then he snares unconspicicous champ and you kill them. Shen can heal you. Shen can taunt enemies. Shen can shield you. Shen is just fine!There are others like Cho'Gath. They are all good.What to say? Rumble can lane almost with everyone. Really. And how about Rumble on MID? I was there just once. Against Nidalee. Not so strong, yeah, but who would say that Rumble would feed on her? Here's the thing: If you are on mid and your opponent is underestimating you, just spit out the Flamespitter (for god's sake, always combo this with Scrap-Shield, just SPAM it!) and kill her. Again underestimating? Well, she's stupid and a noob. Yeah. Of course if the midder is Malzahar or Vladimir, you'll get sweaty. But it's not difficult to defeat them as many would say.I said all I can think of. Let's go ahead.

I use Flash and Ghost.Situational: Cleanse - awesome against Swain, Sion and others that are blocking your way of killing fanatism. Teleport - the ganking tool. It's bad to use it for quick movement, really, it's just silly. Porting to Noxious Trap or Jack In The Box can lead to an easy kill, if not easiest in the game. (Of course you can find some 20HP champ recalling in brush, but this isn't a kill, it's just... I don't know :P) Heal - good for OT - MT. Well err... I don't like it but.. it's possible. Rally - just kidding, this is useless. ExhaustDon't: Rally Clairvoyance Clarity - (kidding, it's awesome, try it!) Revive Promote - if you could.. :D Ignite - it's like meh, but i find it useless late game. You got your DoT Flamespitter. Smite

As I said, Rumble is a harasser. But don't get cocky, because early game, there are minions. They can hurt real bad! Once you get after your minion wave, turn around and go back if you know, that you won't get a kill!

Always use Q+W together! Spam this like crazy and farm minions. Once you get under an enemy turret, try to hit champions with your harpoons.

Rumble is just epic in dominion. However, this build does not focus on dominion, so go find another build.

Im done! The text kinda screwed up and I dont want to fix it... :D However it is still readable i guess.