Level designs!! For me, I won't say hate, but it gets realllllyyyy tiresome after a few dozens.
First few levels....hehe this is so much fun
about the 10th level.....I am going to test and challange the players mind!
About the 20th level.......err...I'll just copy a few designs from the earlier and combine with some new.
After the 30th level.......For Each (Level): copy, paste, mix
Have you considered including less levels in your game, and just making each of those levels more packed with new ideas and perhaps more difficult so it takes the player equally as long to finish the game?
I'm not sure how long a player would be kept interested with copy paste level design.
I personally hate promotion the most. So much so that when I've developed a game I can't be bothered spreading it around and trying to get maximum exposure, I just start right away on making the next game instead.
EDIT: just thought of another one: cleaning up code/logic that you created in a hurry just because you were so determined to get it work, that you didn't care HOW you got it to work! Ugh