These are some of the commands which can be typed inside game for various effects:

Communication Effect
![msg]Global Chat. Broadcasts a message to everyone on the server.
~[msg]Ally Chat. Broadcasts a message to all your townmates on the same server.
^[msg] or @[msg]Global guild chat. Sends a message to all guild members.
$[msg]Party Chat. Sends a message to all party members.
#[msg]You can chat people on your screen while in private chat

Commands Effect
/bigitemsSwitches between small and large ground items
/checkrepShows your reputation
/ekscreenshotToggles screenshot upon ek on and off
/fps or /showframesShows a Frames Per Second rate counter
/gridDisplays a tile grid
/manufillToggles automatically filling required items for manufacturing
/notifymeToggles notification when someone says your name while tabbed out
/showalldmgShows all damage dealt by consecutive damages caused by spellls such as blizzard
/showtimeDisplays a seconds counter
/timestampShows timestamping on chat messages
/to PlayerNameSets the whispering mode to PlayerName
/tooff PlayerNameAdds player to mute list which remains even after logout
/toon PlayerNameRemoves player from your mute list