And no, I'm not trying to be funny by saying Karthus R, or some point and click ability. I mean an actual skill shot that, for some reason, despite having seen it in hundreds, if not thousands of games, you have real trouble dodging it.
For me, it's Lux Q.
I don't know what it is about it, but I've been grazed by this ability more times than I can count. Some times, I'll just derp out and not to try dodge it at all, and other times I'll be so focused on something that I won't notice I ever got hit by it until I notice that my champ isn't moving.
I could move around like fricken Faker in one game, dodging hooks and skillshots a plenty, and then act like I've never played this game before when a Lux is in the next game.
To make matters worse, her Q is normally her initiator for her full combo.........I've eaten enough lasers to compliment a dubstep concert several times over (especially after Lux got that buff to her ult so she can have it whenever and wherever). Oh yeah, I can dodge her ult just fine, it's just her god damned Q for some reason.
So......what abilities are there that you just can't seem to get out of the way of?