Utilize your flamespitter, by standing in the bushes and farm. They do not obtain vision even tho you´re farming, and potentially damaging them in the progress. While doing so, you can use your electro-harpoon to keep the enemy away from yourself, and still remaining visionless in the bushes.

If you think your team is about to enter a team fight, then save your ultimate for that. Because rumble´s ultimate splits the team up, as well as doing alot of damage, and can be the spell that wins the fight.

Another way to be in team fights, is to initiate with your flamespitter and shield, let them focus you, throw your ultimate down, be there just long enough for your team to follow up, and get away by using your shield, for the increased movement, and damage protection

The reason for picking ghost and exhaust are simple. You need the ghost, so you can chase down your enemies, while keeping flamespitter active. The exhaust is the same concept as the ghost, but instead of you gaining speed, they´re losing it.

Rumble´s passive is ´overheat´. Overheat is at some points a blessing, others a curse. In early game, his overheat is quite powerful, therefore keep your heat up, but never more than 60/100. And as soon as you see a chance(this is at lvl 2+), all you do is use your shield, and flamespitter, which should cause you to overheat, and the producing loads of damage early.

Be sure not to be overheated when running away, just wait that 2 sec and your heat drops, pop the shield and escape.

Rumbles ultimate is sometimes a tricky one to place, but just make sure it lays on top of them, as well as on their escape paths, with that, it does damage, and slows your opponents for your team to catch up and kill.