I'm sorry, but I laugh my ass off at this whole "anti-fun" angle.

well, as someone said above, this looks more like 3v3 rather than SR problem... because in SR teemo can be bursted down in no time... as for shrooms, with pink wards everywhere they have no big effort on the game ( if you are stupid enough to chase speed-steroid teemo into the unwarded bush you deserve to die )

singed can be frustrating, but he can be countered easily, especially in ranked when you can counterpick him... he really needs to come close to you do dmg, and he is not that tanky early game...

if you want something anti-fun as you call it, blitzcrank is all time no.1. Not calling OP, but he for the first 15-20 minutes of the game he dictates the pace, you have to dodge grabs, you don't have a choice.

If playing singed is so brain dead. Then why are there videos all over youtube about how to use his "hidden abilities?" The in air melee for fling. Void flings. Invisible poison. Singed is a little more in depth than you originally portray, and being able to use these "hiddens" is what differentiates between a good singed and a derp singed.

AP Yi mid makes the game NO FUN AT ALL. Literally takes no talent to hit Q when there are 3 or 4 minions infront of you, with insane range dealing a good amount of damage. His spell costs barely any mana, and his roaming capabilities are insane when he ults rushes bot and just alpha strike resets both bot laners, oh yeah did i mention meditate?

I love to play singed, one of my favorite champions by far. I think people have the same issue with him they do darius, where they expect a fight to end in seconds whereas these two champions thrive on a prolonged engagement. Singed has crazy regen from his ult and great DoT and slows from his poison, Darius has crazy ramp up on his damage based on how long he's around. The issue is not that Singed is OP, it's that people expect him to behave, and die, like a normal tank. Bursting all their damage on the engage. This is just not the case.

thresh is anti fun.

Darius and Katarina.

Potentially high-damage, low cooldown reset-on-kill ults.

Blitzcrank and Lux

No commitment to get in range.

And now for the rest -- Any champion with True Damage or AA disabler (blind, dodge, etc).