Bukkit

kick:
Description: Kicks a player from the server, all players can be kicked with "kick *"
ban:
Description: Bans the specified username from the server, all players can be banned with "ban *"
unban:
Description: Unbans the specified username, all players can be unbanned with "unban *"
whois:
Description: Returns information on a specified player such as IP etc
freeze:
Description: Freezes the specified player, all players can be frozen with "freeze *"