Tutu
Tuula
Tuvok (after the vulcan character on the Star Trek Voyager tv series)
Tux
Tuxedo
Tuxie
Tuxt
Tweek
Tweek (after the character in the South Park cartoons)
Tweeter
Tweetie
Tweetie-Pie
Tweety
Tweety Bird
Tweezer
Twenty Two
Twerp
Twiggy
Twighlight
Twilight
Twilighteyes
Twini
Twinight (Baseball term)
Twink
Twinken (after the character in "Barney's Magical Adventure" movie)
Twinkie
Twinkie the Dominatrix
Twinkle
Twinkle Toes
Twinkleberry