I'm pretty sure this has been done before but I play lots o' ARAM and I'm bored at the moment.
Feel free to suggest/insult.
Note: This is just my opinion.
Tier 1:
* Nidalee - Obv
* Blitzcrank – His Grab is the reason he's here in tier 1. His knock up, channel inturrupt and AOE only add to it. Sort of falls off later but your team should be strong by then with what you've fed them. (You didn't miss grabs did you?)
* Ashe – Get a Manamune, constantly spam volly, hurl ice birds. Forgettabouteeet.
* Jayce - It's HAMMER TIME. Quite fun, good dmg, tanky.
* Anivia - Nice Aoe/Hard to kill, plus the whole pokemon aspect.
* Zilean – BOMBS
* Master Yi – I don't find him all that special but most people swear by him.
Tier 2:
* Ezreal – Best dance for baiting, his poke is aight too, I guess.
* Lux – Dat poke. Dat tier 1 laugh, Dem rage quits.
* Fiddlesticks – Bouncing birds + huddled enemy teams = caw
* Teemo – No comment.
* Singed – Fling, good laugh and taunt, becomes unstoppable late game. SONGED
* Pantheon – Mad deeps and the ability to suicide.
* Heimerdinger – His beefier turrets take this spot away from Zyra.
* Twisted Fate - Good poke, good suicide, just pretty squish.
* Caitlyn - Range and tarps
* Ziggs - BOMBS EVERYWHERE
* Nautilus – A tier 2 version of Blitz. If there was a Blitzcrank tier list, Blitz would be tier 1 and Naut would be tier 2. Teemo would be somewhere in there as well.
* Kog Maw – Rangiest ranger of ranged ad.
* Sona – Auras and she floats around..?
Tier 3:
(Good, solid ARAM champs, all champions that I don't have listed would appear here.)
Tier 4:
* Rammus
* Skarner – His ult is good, it's just he offers nothing to start.
* Fiora - ^Ditto
* Tryndamere – Once he gets all his items he can solo teams, he just needs a good team and late game.
* Shyvana – Can be pretty difficult to get her ult up. Doesn't do a whole lot of damage.
* Rammus
* Trundle – Almost went into tier 5, but his passive and abilities are solid for ARAM, it's just I've never seen the troll do well.
Tier 5:
(Dodge tier! Just kidding, don't dodge, be a man.)
* Udyr – Crazy easy to kite.
* Nasus – You can build him ap, but ugh. I seem to always get randomed with him too, I HATE YOU NASUS.
Here's an item tier list just because.
Tier 1:
* Aegis of the Legion
* Frozen Heart
Tier 2:
* Locket of the Iron Solari
* Will of the Ancients
* Zeke's Herald
* Abyssal Scepter
* Tear of the Goddess
* Banner of Command
Tier 3:
* Banshee's Veil
* Static Shiv
* Sunfire Cape
* Liandry's Torment
* Hexdrinker