WTF
In common internet parlance, WTF is a three-letter-acronym or netspeak abbrevation for "what the fuck." It is one of few netspeak abbreviations commonly considered "acceptable" for usage on RPGWW, which is notable because of most RPGWWers' strong distate for net slang.
WTF = "hello Zem!"
In July 2003, FlamingDeth posted a thread with the title "I am a chef" saying "Hello". Various other posters replied with various greetings, culminating in ladydragonclaws saying "WTF" in a large font. (The thread is so old that it has been pushed off of ezBoard.)
Zemyla took the joke and ran with it, immediately using "WTF" as a greeting in the chats. It caught on quickly, and now WTF is considered one of Zemyla's calling cards. WTF has also had several "alternate definitions" proposed over time, including "welcome to Funkytown."
WRF
"WRF," an easy typographical error of "WTF," is occasionally used in a mocking manner that imitates poor usage of netspeak (see [Lamer]). It is commonly used as part of the phrase "WRF are this dumb shit," an epithet popularized to some extent by Captain Pervy.