Tier 1: Alistar, Amumu, Anivia, Annie, Ashe, Blitzcrank, Cho'Gath, Corki, Dr. Muno, Evelynn, Ezreal, Fiddlesticks, Gangplank, Heimerdinger, Janna, Jax, Karthus, Katarina, Kayle, Malphite, Master Yi, Mordekaiser, Morgana, Nasus, Nidalee, Nunu, Pantheon, Poppy, Rammus, Ryze, Shaco, Singed, Sion, Sivir, Soraka, Teemo, Tristana, Tyrandamere, Twisted Fate, Twitch, Udyr, Veigar, Warwick, Zilean.
Tier 2: Taric, Kassadin.
Tier Deserves-Deletion-From-The-Game-FFS: Gragas.
So you see, all of the champions when played well can prove to be fairly devastating to the enemy team or overwhelmingly helpful to your own. Different combinations of champions are, as common sense would have you believe, more effective than others. Just because you either A.) Suck at a champ or B.) Have never seen a particular champ played well, doesn't mean that the champ belongs in a low tier. Tier 2 is not far off from tier 1 in my order of ranking. I just feel the champions in tier 2 are a little underpowered compared to the rest- feel free to debate me, I won't read it.
Delete Gragas. Srsly.
*edit* this community is horrible