Here is a list of all the user modes which are available for use. An example command for setting a mode on yourself is: /umode2 +D

a = Is a Services Administrator (IRC Operators only)
A = Is a Server Administrator (IRC Operators only)
B = Marks you as being a Bot
C = Is a Co Administrator (IRC Operators only)
d = Makes it so you can not receive channel PRIVMSGs (Deaf)
D = Makes it so you cannot receive private PRIVMSGs (Deaf to PMs)
g = Can read & send to GlobOps, and LocOps
G = Filters out all Bad words in your messages with <censored>
h = Available for Help (Help Operator)
H = Hide IRCop status in /WHO and /WHOIS. (IRC Operators only)
i = Invisible (Not shown in /WHO searches)
N = Is a Network Administrator (IRC Operators only)
o = Global IRC Operator (IRC Operators only)
O = Local IRC Operator (IRC Operators only)
p = Hide all channels in /whois and /who
q = Only U:lines can kick you (Services Admins/Net Admins only)
r = Identifies the nick as being Registered (settable by services only)
R = Allows you to only receive PRIVMSGs/NOTICEs from registered (+r) users
s = Can listen to Server notices
S = For Services only. (Protects them)
t = Says that you are using a /VHOST
T = Prevents you from receiving CTCPs
v = Receive infected DCC send rejection notices
V = Marks the client as a WebTV user
w = Can listen to Wallop messages
W = Lets you see when people do a /WHOIS on you (IRC Operators only)
x = Gives the user a hidden hostname (security)
z = Marks the client as being on a Secure Connection (SSL)