This is my first ever guide, and I feel it is needed as, at the moment, Rumble is a very under rated champion, who has incredible potential. Saying this, he is limited in some ways, but like every champion, excels in others...

Runes are pretty standard for most casters, with a couple of changes. As per usual, utilizing the magic penetration marks. Seals, I have found the best to use are dodge, as Rumble obviously doesn't receive any benefits from mana regen. Glyphs are more up for discussion, I have found the both CDR and flat MR are viable, personally I prefer the extra magic resist early game (makes farming a lot easier if some of the pokes are a little less punishing). Finally as always, bar a few exceptions like roaming champions, and Ashe, flat HP quints are invaluable.

Pretty standard for a tanky caster who doesn't benefit enough from the utility tree. The obvious route is to get the 15% magic penetration, and then the rest of the points go in to the defence tree. Can sacrifice the extra defence for attack, by going for the full 21 in attack, and gaining the 4% damage boost, but doing this wastes some points you don't need to on attack damage ad critical damage. So in my view, isn't worth it...

Items I can see a few people disagreeing with, especially my early choices. A lot of people like to rush Rylai's with Rumble, which is understandable, the extra damage, and survivability, and slow are amazing with Rumble, for both getting away, and for getting kills, so definatly get it at some point in your build. However, Will of the Ancients is such a powerful item (aura is amazing for your team mates too) and the spell vamp does still stack with one Hextech Revolver, and given how cheap these items are, this gives you a LOT of burst damage mid game, and a LOT of survivability. With this build, provided you position your ulti correctly in a team fight, you will be virtually indestructible for its duration, with your flame thrower on, and your shield, with 45% spell vamp, you will be getting around 200-400 hp back per second dependant on how many people you hit your ulti on. This should allow you to stay alive, and also tackle people who think you look weak on low hp 1v1, but they will find it a lot more difficult, often underestimating and therefore giving you easy kills. Before you disregard this build, give it a go, and see for yourself, as long as your smart with your positioning, then this is so OP.

Pretty standard combination, like with all high elo games, flash is so necessary, ignite I like for finishing off kills, but against heavy cc teams, if you feel merc treads aren't doing enough, can always swap for cleanse, or exhaust against heavy auto attack team, but flash is very useful :)

Hope you enjoyed reading my thoughts on Rumble, looking forward to any feedback!