Wear your hat if you want to, I'll avoid striking to your head area (it wouldn't be worth the effort anyway - what with all that hair providing padding! )
Microsoft Paint in Windows 7 - the fact that it won't let you easily draw a series of connecting lines, it has to assume that if you click near an existing line, you want to move that line rather than draw a new one. It makes it really difficult and annoying to draw simple MS Paint diagrams. Stupid Microsoft.
GRRRRRRRRRRRRRRRRRRRRRRRRRR!!! Flaming stitching in the drivers seat of my car is coming apart exposing the spongy guts!!! GRRRRRRRRRRRRRRRRRRRRRRRRRRRRR!!!
also books written in an intentionally obscure manner. even with subtleties, i much prefer directness, not passages written in unintelligible ways and that appear to give out inconsequential data.