verflixt! (Tymewalk): A German slang word roughly equating to "darn it!"
JINX (CG started it but it spread): Something said when two users talk at the same time, usually followed by "YOU OWE ME A SODA" or some variant tl thhereof
Блин! (TheHockeyist): Russian word for pancake, usually used as a filler swear word (pronounced "blin")
VERHEXEN! (Tymewalk): German form of "JINX!" (literally curse), usually followed by "DU SCHULDEN MIR EIN KEKS" (you owe me a cookie)
NYEH HEH HEH (Faressain): Random laughter.
GERSH DERN IT (CG): Gosh darn it but lighter.
DAGNABBIT (Tymewalk shamelessly stolen from DGC's comments): Similar to gosh darn it!T
Ninjaed/Ninja'd (most people): When you outpost someone by a very small amount of time (sometimes even zero seconds)
Espio'd (PrincessPandaTBG): Same for "ninja'd"; derived from Sonic the Hedgehog character, Espio the Chameleon, who is a ninja
Kek (coolman, shpore): replacement for 'lol'
<MEOW> (Smiley): Used to self-censor words.
(curse), (Valar Morghulis) or <hiss> (Faressain): Also used as a filler self-censor word. Curse is self-censor while Valar Morghulis is so-said "All men must die." Actual debut of <hiss> was in TTA, but eventually replaced <curse>.
[bork] (Floofy) - used as filler self-censor word.
Custom Emoticons - used to show feelings (only used and made by the2000)