Hello people thanks for reading my first ever guide on mobafire. I decided to make a guide because I felt I was doing very well with my builds. For example here's an image.]
I decided to throw in a Ranked match to see how well I'd do against a tough team. As you can see this guide isn't a load of **** ;-)
Oh and this picture is for those of you who believe that Rumble's damage suffers late game.
I used to have CDR runes and after doing the math you guys are correct that it's not entirely necessary and that Magic Pen is way better. As for runes now I go for Magic Pen, a lot of HP. This allows me to gain a big advantage early game. At level 1 I have OVER 800 HEALTH. This allows you to be more aggressive with your flamespitter while harassing.
The masteries are the standard 9/21/0. You definitely need the spell penetration and the mastery for exhaust is very helpful. In DEFENSE the 48+ HP from veteran's scars is going to really help your early game too. That combined with your HP runes will make people not even think about harassing you.
Now here's the interesting part. You definitely want the crystal scepter first because you want the HP the AP and the amazing slow passive. The slow + the constant flamespitter spamming gives an almost infinite slow like Ashe. This gives Rumble 3 effective slows making it very hard to escape him. After you get Rylai's Crystal Scepter, what you get next is based entirely on the situation of the match. Get Randuin's Omen only if the opposite team is filled with DPS champions or if they have a fed DPS champion. The Health+Cooldown+Armor is perfect for Rumble. Remember that Rumble doesn't necessarily need a lot of AP to do a lot of damage. Of course get the Force of Nature when the other team is filled with spell casters. The movement speed works well with Rumble while the Health Regen really helps with your laning to stay longer. I get the abyssal scepter when I see that the other team has purchased a few magic resist items or when your team has a lot of spell casters. Situational items would be Void Staff or Lich Bane. Feel free to get Rabadon's Death Cap when you notice that the other team isn't damaging you at all.
As for the skill sequence. Definitely max flamespitter first. It plays as your farming spell as well as your harassment spell. Because it's so spammable I use it constantly to deny the other team by not letting them get close to the minions. Be sure when you become aggressive to use your Scrap Shield before using flamespitter. Try to maintain over 50% Heat so you could do more damage. You will love the speed boost and shield from Scrap Shield. Definitely max your harpoon last but make sure to keep 1 level in it at level 3. It's very helpful for free ranged harassment, free slows (especially when you kite), and to help keep up your heat bar. Make sure when you're hitting their towers, SPAM THE **** out of your abilities. You want to overheat so that your basic attack will do a lot more to destroy towers faster. Your ultimate is tricky to pull off sometimes. Make sure to always keep it handy for ganks. Set up a gank in a bush with your teammates and it will be MUCH easier to get a good ult off. It forces the enemies to stop attacking so they could move away from your ult. By that time it would already be too late as you are infinitely slowing them.
My reasons for Exhaust and Ghost. For Exhaust, use it when you want a champion to take the full brunt of your flamespitter or ult. Your teammates will LOVE your slows. Ghost is for a similar reason. Both for escaping and chasing. Use it to go in range with the enemies to start crazily slowing them. Or use it with your scrap shield to make a an easy escape. With your mercury treads, you really shouldn't have too much trouble especially because you can slow your chasers by kiting them with harpoon.
Basically, I make people think Rumble is an overpowered champion. Hopefully with this build, you guys can do the same. This build works well for both 3v3 and 5v5. Just make sure you have dependable teammates and you'll maybe even carry.
NOTE: Rumble does steal A LOT OF KILLS with his flamespitter because of the constant damage so be careful.
Pros / Cons
Works extremely well in ganks because he has area of effect spells
Very good harassment abilities
Can 1v1 a lot of champions
Hard to escape ganks but very possible
Late game his damage suffers a bit if not fed
Mostly Close Ranged Spell caster
Just make sure you last hit a lot of minions while denying your enemies. Try not to use flamespitter as much because actually I've noticed it makes it a lot harder to last hit minions early game. PRACTICE MAKES PERFECT!