It has to be when me and my friends were playing 4vs4 on halo 2, I can't remember the map but I was just sitting in a dark corner behind one of my friends for Atleast 5 minutes, when I got bored of waiting I just pulled out the energy swirl and stabbed him in the back, the shout of me scaring him was deafeningly hilarious, and since then every corner is checked by him in every game!