I'll join the train.
Started to work on mine about 10 months ago, but I always find new stuff that I want to add so basically the completion % has been steady for months D:
Weapons (sprites/sounds/mechanics): Only missing 1 out of 8. I have a plan, but not too sure to start working on it yet.
Enemies (sprites/sounds/behaviors): I have over than 37 monsters, 9 neutral creatures and 7 npcs, but my brain decided that the project needed fishes, so now I'm stuck at creating a proper fish AI...
Pickups / Items: Missing some powerups.
Levels: Last thing I'll do.
Textures: Got only a few.
Sound effects: Ripped off some nice sounds here and there, but I'll need a lot more probably, so I'd say 30% (?).
Music: Still need to find some eerie atmospheric midis.
HUD: Barely started.
Fonts:
@Desfar I feel you
Title Screen splash image: I plan on making a TITLEMAP, I already have the thing in mind, but never started.
Options screen splash image: Yet to think about.
@Burgish Maybe you're missing GLDEFS, DECALDEFS and other stuff that can enter in a "Visual effects" category? If you're touching that, of course.
Or scripting, like ACS, KEYCONF or Cvars