Whenever a Terrorist (or CT) commits suicide by falling.
Watching a player die by knife after missing with an entire weapon magazine due to panic. Hilarious if they pull out their pistol and miss that as well.
In Global Offensive, the Terrorists on cs_office. They basically amount to scene kids rebelling against The Man. Their lines are also hilarious. They realise how fucked up the situation now is and how screwed they are. They try to put a brave face on it.