Hello, this is my first guide on Mobafire. I've been playing Rumble for quite some time now and I really love him. I play 3v3 Rumble and 5v5 Rumble. Both of these game modes are really fun for Rumble. I always play Rumble mid/solo lane, because it's easier for me to harass in 1vs1 rather than 2vs2. Here I will show you how I play..
Rumble, the Mechanized Menace.

Why should I buy Doran's Shield?I buy Doran's Shield for Rumble, because for survivability for when you're laning. You need the armor, HP, and HP regen is great for laning.

Why Mercury Treads? Why not Sorcerer's Boots?Well, first off, Mercury Treads helps you flee from towerdives, teamfights, and even ganks. Plus you already do tons of damage without the +20 magic penetration.

How does Rylai's Crystal Scepter help me?Rylai's is my favorite item as Rumble because, it gives plenty of Ability Power, Health, and gives your skills even more slow for chasing down those nasty runners.

Why should I get Sunfire Cape?Sunfire cape is the perfect compliment to your Flamespitter spell. It gives you additional damage, while chasing your enemies with your flamethrower. Plus it's a great tank item.

Why Zhonya's Hourglass? Why not Rabadon's Deathcap?Zhonya's Hourglass is a great tank item with a lot of ability power, that also gives you 2 seconds invincibility for when you're in danger and a teammate is a couple of seconds away to come assist you.

WTH?? Guardian angel? Why not more AP items?Guardian Angel is one of the best tank items in the game that gives plenty of armor and some magic resist, which is important for Rumble so he can deal massive amounts of damage and not die.

Why should we get Banshee's Veil?If the game is taking that long, sell your Doran's shield and replace it with Banshee's Veil. Since we don't have very much magic resistance in this build, we can get more magic resistance, if the other team has casters. Banshee's Veil's passive can block a negative spell every 45 seconds. So if the other team had a stunner like Evelynn, you can get away easily or fight back easily without having to wait that 2 seconds of stun.

I grab thisand this, because Rumble doesn't have escape mechanism. This would also help his survivability, and for tower diving once you reach level 6.

Greater Mark of Insight (Magic Pen) - These are great for any casters
Great Seal of Evasion (Dodge) - This helps your nimbleness skill mastery have a higher chance so you would have your speed increased by 10% for 5 seconds.
Greater Glyph of Shielding (Magic Resistance/per level) - The magic resistance per level is great because you're high on armor but low on magic resistance late game.
Greater Quintessence of Swiftness (Movement Speed) - The movement speed quintessences are great because as Rumble you want to try and stay alive as long as you can, since you can easily defend towers with your ultimate and it also helps you catch up to your enemies.

This is my score after I played with Rumble with this build. I even had BETTER matches like 900/1 :)

I will update this build soon. Don't have enough time right now, thanks for reading!