Hmmmmm... interesting question.
I *thought* I'd love the oil-paint (due to liking it best of the traditional media I've tried) and the airbrush (due to liking it so much in Painter Essentials). However, the airbrush doesn't work much like the PE one, so I was initially disappointed... UNTIL I tried the Chalk tool! It's fantastic, even better than the PE airbrush. Along with occasional Knife blending work, Chalk has become my favorite *creation* tool... along with nigh-constant use of the Eraser. I admit it :-) The Roller is good for quick backgrounds with a bit of texture, and Stencils are occasionally astoundingly useful. Really, really really saved the day more than once. Way more useful than I'd have thought.
On the flipside, I have only ever used the Glitter gun when I'm dorking around making pseudo-abstracts to blow off steam after doing something intense, like the 30-second drills at posemaniacs.com. I've seen how people get fantastic results from it though, so it might come in handy some day. I just don't do that kind of texture, usually, so... we'll see. Oh yeah, I don't think I've done more with the Paint Tube than try it out once. And I've never been much one for pencil, and the time or two I used it I messed up and wound up with not-pencil lines :-/...
My "future gotta figure it out" list is currently the Felt Pen... the astounding magic that misterpaint accomplishes with it is inspiring. And I keep meaning to try to figure out Sweedie's advice about using the Crayon tool as a blender.
And I think that's everybody :-) at least for the current ArtRage... can't wait to meet the new crowd!
Edit: Someonesane, those are some great images!
WARNING: ArtRage can cause serious loss of time, and excessive smiling! Use with care! Frequently!
“All creativity is an extended form of a joke.” – Alan Kay