The error of the day came from the planet php - Parse error: parse error, unexpected T_PAAMAYIM_NEKUDOTAYIM. An unexpected WHAT? :) (pops up if you have double semicolons).
Next one came from vistas darkest side. I took this screenshot some time ago but the picture got lost in the infinity of my mobile phones memory card. My laptop came with preinstalled Vista. One day, I was just minding my own business, playing some mp3s, chillin... and this baby popped from nowhere and rendered my system unusable. I never, and I really mean NEVER ever, in my entire windoze career saw an error like this. Enjoy! :)
(System died so bad, that even taskmgr.exe couldn't be started).