This build for Rumble is based around his Junkyard Titan passive ability, which makes his normal attacks stronger when he overheats.

Items

For my items, I go with an Amplifying Tome and a Health Potion to start, giving me some early game ability power. I then build that into a Hextech Revolver for some spell vamp and some more ability power. Next I buy Ionian Boots of Lucidity to speed up my movement speed and to allow me to spam my skills more. I then turn my Hextech Revolver into a Hextech Gunblade, so I can start dealing some decent damage during Junkyard Titan.
The next item I get is a Nashor's Tooth, so I can start making the most of the bonus damage from Junkyard Titan, as well as allowing my skills to do more damage. After that, I buy a Rylai's Crystal Sceptre, as it gives a good slow, especially when combined with Flamespitter, to make it an AoE slow.
The eighth item I buy is a Sheen, as you can overheat, go into Junkyard Titan, and then hit something and still do the damage from the Sheen proc. The damage is massive when combined with the bonus damage from Titan. Then I build another Hextech Gunblade for some more damage, ability power, lifesteal and spell vamp. Lastly, I build my Sheen into a Lichbane, to make the most of the proc and add some more late-game ability power.

Runes and Masteries

I go 21/9/0 for maximum damage early game, because people will not expect you to hit as hard as you do.
It's the same with runes, building for maximum early game damage, as if you get fed early game you become and unstoppable force late game. The armour seals are just so you can take a bit more damage while initiating early game.

Skill Sequence

Like all good Rumbles, you should be keeping your heat at around 55, so you can use all your skills with the Danger Zone bonus before overheating. This is especially important with this build, as you do quite a lot of your damage while in Junkyard Titan.

When casting your spells, always make sure to use Electro-Harpoon last, so you can stick onto your enemy as long as possible during Junkyard Titan.


Thanks for reading my guide, and I hope you have fun with it!
- NinjaSprite