"Tiax moves! Make way!"
While I have not had the pleasure to meet this character yet in Baldur's Gate (both in the computer game with the same name, and the city in the game itself where this character resides), he seems like an extremely interesting character - not as interesting as Minsc or Xan, but interesting nevertheless. So, I rely on sources.
"Has Tiax mentioned he is going to rule? 'Tis inevitable."
Tiax is a chaotic evil gnome cleric/thief (worships Cyric). He doesn't appear to talk too much of what he has done in past, but that's okay, the lack of talking of past is compensated with throughout discussion on what he will do in future. He also has a habit of talking in third person.
"As it should be. Tiax was destined to lead."
Tiax appears to be a bit of a megalomaniac, with a clear idea that he is GOING TO RULE. And he babbles about this all the time.
"You cup shot mutton head! Tiax will slap ya silly! When he rules."
Tiax also appears on Baldur's Gate soundtrack: He's in three different mixes on the hit single "Tiax Rules!", clearly not at all bad pieces of electronic music! (To hear the "Eclipso Mix" of this song along with the Soldier Trance, view Baldur's Gate credits. The MP3 is also available from Bioware's website.
(DyRE says re Tiax: Tiax has a cameo in Baldur's Gate II as well. He's not a playable character in BG2 but still amusing. When attempting to brand the player character with a 'mark of shame' he mistakenly shrinks his underwear three sizes.)
"Ya little monkey spanker."