Retrogame romhack pet peeve.
The very definition of diappointment is when I find an interesting-sounding romhack and see that they've spent all kinds of time with gameplay modifications and level edits and the like... and then decided that since they can't do graphics worth a damn they're still got to change _something_ and thus replace the fonts (and frequently, just the numerals). The results are never good.
I think I'd pay some of these folks to let me do a better job... but there are so many decent bitmapped fonts out there that they already didn't bother choosing, so why would they want anything I made?