osu!:
-Notes right after spinners (mainly those that aren't in the center because I always find myself too far away from the note to hit it)
-Odd patterns with stacking (it's fine if it seems to go with the song, but there are some things that are unnecessary and hard to read)
CtB:
-Spinners right after notes (I think the note is part of the spinner and miss it D:)
-Big back-and-forth 1/2-beat jumps
-Maps that are full of hard-to-hit sequences that make me want to pull my hair out (
http://osu.ppy.sh/b/42152)
Taiko:
-Seemingly random patterns
-Really fast 1/4 beat streams that contain an impossible-to-hit mixture of red and blue notes
-Long streams of 1/8 notes (as well as short 1/8 streams on anything above ~130 BPM)