Version 1.0 Created 4/27/2011 - Rough final completed.

UPDATES
Version 1.0.1 Updated 4/27/2011 - Fixed Masteries tree to exclude Strength of Spirit. Thanks drsoup!

PLEASE NOTE: I do not use any pictures or animations. I apologize for this but it doesn't mean that this guide isn't firm and useful. I will add these things later as time goes on. Do not down-rate because you don't favor some reading. This build works. I dare you to try it. ;)

Thank you for taking the time to read my guide on Rumble. Our league's newest champion.
Rumble is a very unique and fun AP based champion. You can play him to have incredible survivability and to be more tanky, which I have done in this build. This build also helps him focus good AP items that make him a huge asset to the team and every team fight. I hope you enjoy reading this guide. Please rate/comment!

PROS:
Great Survivability in Team Fights
Decent AoE damage with Flamespitter and The Equalizer
Very good slow capability with Harpoon, The Equalizer and great synergy w/ Rylai's
Deceptively powerful with decent AP items

CONS:
Has issues with certain ranged champions and AP nukes
Can be difficult to farm early game as last hitting is difficult with Flamespitter
Keeping track of/knowing when and when not to over - Heat can be difficult

Rumble relies on Heat to use his abilities. Every move will give Rumble 20 heat, which slowly decreases over time. If you're over 50 heat all of your abilities have a heightened effect. Mastering his Heat gauge is the most important thing to be able to do to play Rumble efficiently. You need to make sure that you're frequently in the Danger Zone while harassing with Harpoons and Flamespitter, but be sure to not Overheat during team fights.

Overheating has certain benefits that need to be mastered as well. It provides additional magic damage on all of Rumble's melee attacks but prevents him from using his abilities until he has cooled off. One primary use of this is when pushing a tower. It can provide additional damage to get the tower down quicker. Be sure not to overheat while attacking a tower if enemies are nearby however. They could easily take advantage of that opportunity since you will no longer have your Scrap Shield for speed buff and defense.

Your role as Rumble is simple. Slow the enemy team and harass/stack damage with Flamespitter/The Equalizer. You can easily use your ultimate to force enemy carries out of brush to avoid ganks or out of your teams face during a team fight (lowering their effectiveness). Focus on this strategy and remember that you're resilient and are building for survivability but that does NOT make you invincible! Your other primary focus is staying alive. Use Scrap Shield often to help escape and prevent enemy ganks.

The Rune choices I've made help coincide with his Masteries and play-style.

Magic Penetration Marks help early game. With your first point going into Flamespitter it's very important that you have this early game edge against your opponents. Flamespitter can do some unexpected damage that most enemies won't even realize until it's too late. It's also your main farming tool so it's best to support it in any way that you can.

Dodge Seals help tremendously with your Masteries since you're speccing into dodge. This gives you a heap more survivability at level 1.

Magic Resist Glyphs are again focusing heavily on his survivability. One of his main weaknesses are ranged champions. Most AP nukes should be countered with MR whenever possible.

I use a very straight forward approach here. 9/21/0

I get the magic penetration and improved exhaust from the offensive tree and then focus heavily in the defensive tree. Making sure to get the improved dodge and increase to AP.

You can play around with this a bit but I like this focus of defense heavily and it's where Rumble should be played even if you're focusing more heavy AP items.

During a lot of the games that I've used Rumble or seen Rumble being played there has been a huge speculation on going pure AP. Some friends and I have attempted a full AP build and found that losing survivability really hurts this champion. So I've decided to focus AP second to survivability and it's worked out beautifully.

The first key item you need to focus and get quickly for obvious reasons is Rylai's Crystal Scepter. The item is just amazing. It provides health and survivability along with a hefty amount of AP and adds a slow to your abilities. Being able to slow an entire team in a team fight with Flamespitter is just AWESOME.

Once you get your scepter finish up your Sorc's shoes and then work towards getting Force of Nature. Once you have FoN you will be incredibly resilient and survive very well, the MR is gives is also incredible and nothing to scoff at. This will be around Mid-Game.

Now that the game should be entering the later phases its time to start building your Deathcap. Deathcap takes you from being a resilient harasser to a finisher. You start blowing up your opponents with your ultimate and the slow you provide will make it almost impossible for your enemies to escape.

If the fight is not yet won you can build a Gaurdian Angel to round out this build. It work's incredibly nicely because it takes some of the focus off of you which allows you to really dig in and hurt your opponents with prolonged Flamespitter action. You can also use this and your final slot for counter-pick gear against certain teams.

Alternate gear for certain situations that should be noted are below:
If you're facing down a heavy AD/melee team rush yourself a Thornmail before getting your FoN and switch your boots up to Ninja Tabi to combo with your Dodge Masteries. Making it hard for champs like Master Yi to take a chunk out of you without being punished by Thornmail and Flamespitter. ;)

If the enemy team has numerous amount of CC you should focus Mercury's Treads over Sorc's shoes. Also look into getting Banshee's Veil before your FoN. Being able to stop an opponent's stun is crucial to survival! Quicksilver Sash can also be gotten later in the game if you're still having issues with CC or suppression ultimates like Warwick's and Malzahar's.

Nothing too special here. I max Flamespitter first, alternating it with Scrap Shield. Getting 1 point in Harpoon at level 4 and maxing it last. I take his ultimate whenever available and finish Scrap Shield second. The move buff and added defense on activate is really good for survivability.

On Rumble I chose Exhaust and Ignite.
Feel free to experiment with other abilities but I find that these two work well together with this build and his spec. He already has a built in movement buff with Scrap Shield so I argue against taking Ghost, but it's really good for getaways.

Flash is always useful as well so that's a good substitute.

I would NOT recommend: Clairvoyance, Rally, Clarity, Revive or Fortify (although this can be situational)

Those simply do not support his play style at all. The remaining all serve a good purpose and depending on how you chose to play him may play a good role for him. Smite is only viable if you're jungling which I have NOT yet tried on Rumble so use/jungle at your own risk. ;)

To clarify the focus of this build one last time: Survivability

Your role with Rumble to to stack some decent damage on your opponent's using Flamespitter, also providing added slow with Rylai's Crystal Scepter and your Harpoon. Your main focus are the enemies weaker/squishier champions. Make sure to use your ultimate on/near the enemy team in a way that will force their carries to run out of its AoE and place themselves in range for a beating by your teammates. Other then that be mindful of your lane and focus on not dying.

I hope you enjoy this build. Please comment with any feedback that you may have!
See you on the fields of battle!

-HerpDerpMeh