When a battle is about to start in matchmaking in Halo, I do my very best to go after and absolutely make the round hell for:

(Priority list, there are two tied for the 2 spot)
1. People who say racial slurs
2. Kids
2. People who make fun of my gamertag (kills are often followed up by teabagging or me beating the out of their corpse)
4. Kids
5. Anyone with a reference to weed, being a pimp or thug, or 69 in their gamertag
6. Kids.

Honestly. I hate it when kids play games that they aren't mature enough to play. It seriously pisses me off. It's rated 'M' for a reason--given, many of the players my age are very stupid as well.