The list of available usermodes:

a: services admin, allowed to /samode
A: server admin, allowed to use /mod*
c: no color in private messages
C: no ctcp in private messages
h: user is a helpop
H: user can see hidden things (ip, secret channels...)
i: the user is invisible
n: Routing notice messages
o: operator, allowed to /kill,/kline,/gline
p: hide idle time in /whois
P: do not receive any privmsg/notice except when /accept is used
r: registered
R: the user does not want to get messages from unregistered users
w: channels are hidden in /whois
x: the user hides their hostname
t: Translation mode (greek to greeklish)
z: Dccallow all users