A personal peeve of mine is when players with rediculous user names log in and start spouting obnoxious and/or racist crap into a chat channel.
[2Cool4U] /\/\3+@5p@z0r: - OMG n00bed again.
)(^!()@*(#^^$)@(# [Perl Rulz]: - Does anyone else on here have an XBLA account? I heard that games on there can be really cheap.
. . : : = [ L 3 3 t  +  H @ x 0 r ] = : : . .: - STFU n00b. STFU n00b. STFU n00b. STFU n00b. STFU n00b.
It's all fun and games until you try to /mute them, which requires you to somehow memorize their handle and type it in *exactly* in order to mute them.
It would be nice to have this re-coded to accept wildcards like so:
/mute *L 3 3 t*
... or just added as a first-class menu option much like kicking a user or changing the map. Either would help prevent users from hiding behind their nicknames when acting like complete twats.