NOTE: THIS GUIDE IS STILL UNDER CONSTRUCTION

Rumble the Mechanized Menace has been one of my favorite champions to play recently. He can be built in several ways, like most champions, however, this is the build I have found works best in my limited experience with him. This is my first guide, so I might miss a few things, but I hope this helps people play Rumble a little better.

Lore
Even amongst yordles, Rumble was always the runt of the litter. As such, he was used to being bullied. In order to survive, he had to be scrappier and more resourceful than his peers. He developed a quick temper and a reputation for getting even, no matter who crossed him. This made him something of a loner, but he didn’t mind. He liked to tinker, preferring the company of gadgets, and he could usually be found rummaging through the junkyard. He showed great potential as a mechanic. His teachers recommended him for enrollment at the Yordle Academy of Science and Progress in Piltover, where he may very well have become one of Heimerdinger’s esteemed protégés, but Rumble refused to go. He believed that Heimerdinger and his associates were "sellouts", trading superior yordle technology to humans for nothing more than a pat on the head while yordles remained the butt of their jokes.
When a group of human graduates from the Yordle Academy sailed to Bandle City to visit the place where their mentor was born and raised, Rumble couldn’t resist the temptation to see them face-to-face (so to speak). He only intended to get a good look at the humans, but four hours and several choice words later, he returned home bruised and bloodied with an earful about how he was an embarrassment to "enlightened" yordles like Heimerdinger. The next morning he left Bandle City without a word, and wasn’t seen again for months. When he returned, he was at the helm of a clanking, mechanized monstrosity. He marched it to the center of town amidst dumbfounded onlookers and there announced that he would join the League of Legends to show the world what yordle-tech was really capable of, without hiding behind a foreign banner.

"Ugh, it’s gonna take forever to scrape your face off my suit!" –- Rumble

Pros
-Hits hard and fast
-His Ult DRASTICALLY changes teamfights
-Amazing AP ratios and base damage on all his abilities
-Once he hits Level 3, he harasses really well provided he can stay in the Danger Zone

Cons
-Until he hits Level 3, his harass does NOTHING
-A bit squishy, especially early game until he gets the defensive stats from Zhonya's and Abyssal Scepter
-His ult can be hard to aim sometimes

Greater Mark of Magic Penetration
I like these for any AP Based Champion simply due to the fact that it effectively reduces any Champion's Magic Resist by 9. At Level 1, most Champions will lose 1/3rd of their Magic Resistance and it will only get worse from there.

Greater Seal of Vitality
These will give you an extra 9 health at Level 1, then 9 more per Level after that. That little bit of health means everything during laning and early ganks.

Greater Glyph of Scaling Ability Power
A little more AP doesn't hurt.

Greater Quintessence of Ability Power
3 of these guys combined with the Glyphs will give you the AP of an Amplifying Tome right off the bat. Combined with the 10 MPen from the marks and you'll hit hard.

For masteries I take 9/21/0, taking AP, Cooldowns, and Magic Penetration in the Offense tree while focusing heavily on evading damage in the Defense tree. I max out Resistance and Hardiness for a little early game Magic Resistance and Armor. I then take only 3 ranks of Evasion to increase my dodge chance by a little bit, then I take the 1 rank of Nimbleness and 3 ranks of Harden Skin. Since Rumble gets up close, he's going to need to block a lot of physical damage. I then take 4 ranks in Veteran's Scars, giving me an early game health boost, 3 ranks in Ardor for the AP boost, and Tenacity for the damage reduction all game.

These masteries allow Rumble to get up close early game while allowing him some survivability without spending lots of gold on getting it.

The build at the beginning says you won't keep your Sorcerer's Shoes through the whole game. That's wrong and I don't know how to fix it (if a professional MOBA-er would help I'd appreciate it =D).

You'll start off with Boots and 3 Health Potion. You're going to want to stay in lane until you have 1900 gold. After that, you'll want to build Sorcerer's Shoes and a Giant's Belt. This will make your attacks hit a little harder and help you stay in lane a little longer/gank more effectively. After the Giant's Belt, you'll want to build a Haunting Guise and Rylai's Crystal Scepter.

I'd like to take a quick break from the item build order to explain my reasoning behind using a Haunting Guise. Haunting Guise gives 200 health, 25 AP, and 20 Magic Penetration. Combined with Sorcerer's Shoes and your runes, that's almost 50 Magic Penetration. That's enough to bring most champions down to 0 Magic Resistance, if not into the negatives. That item packs a lot of early game punch for a low price, but its effectiveness drops off later.

Anyway, back to the build order. After building Rylai's Crystal Scepter, you are going to want to build Rabadon's Deathcap for the huge AP bonus. At this point, you'll have roughly 250 AP, which will melt any non-tank champion almost instantly. After this, you will build an Abyssal Mask for effectively 70 Magic Penetration, and then Zhonya's Hourglass for Armor and Ability Power. At this point, you'll have 6 items, so you will sell your Haunting Guise and replace it with a Hextech Gunblade. The Haunting Guise doesn't give you enough power at the later stages of the game, even with the magic penetration and the Hextech Gunblade will help you when you are Overheating, while the Haunting Guise will not.