Status/progress bars. Y'know, those bars that fill up when downloading, installing, or for whatever reason have to wait on the computer. There's several reasons for this:
It might load to 83% fairly quickly...then take it's sweet ass time.
The bar gets totally full to 100% Yea! But wait, there's more. Here's another empty bar to replace it.
Granted, sometimes they have 2 bars...the top one being the sub-folders and bottom being the "main" one. But don't count on that one being the only one either...it often gets renewed with another "main" progress bar just as easily, further increasing disappointment and impatience.

Oh well...they don't anger me. Just a peeve. Guess they're still better than an hourglass!