This is a detailed banning tutorial for Mac users:
1. type -console at the end of your Halo launcher
(no spaces, including the - )
2. start halo and in the options window enable the console.
3. start a server
4. type ~
5. type sv_players
(there will be a list of numbers to the left of player names)
6. type sv_ban (dont press enter yet)
7. type the players (you want to ban) number at the end of sv_ban
the player should be banned now.
How To Unban:
1. type sv_banlist (a list of banned players will appear)
2. type sv_unban (dont press enter yet)
3. type the players NAME at the end of sv_unban
the player should be unbanned now.
Its the same with kicking, just type sv_kick instead of sv_ban
Tip: you might want to print this out.