Put me down for the Yellow Dunlop Torex's also. Man, that seems to be a popular pick. I used a thinner pick for a long time, but found when I started practicing seriously and trying to get things like pinch harmonics, that I need a something thicker... I just tried a whole bunch, including those cool-looking lexan pics. In regards Sebastberg's post, that's pretty much spot on for my rationale as well. One thing I noticed with really thick picks is that they tend to produce a lot of string noise (this is probably also due to how I hold the pick). I settled on the Yellow ones.. just a tiny bit of flex which I like, but comfortable, rigid feeling and minimal string noise.

Just go get a bunch of different sizes and thicknesses, put them in a little bowl where you practice. in a month, the ones you can't find are the right ones for you (hint... check the lint catcher in your dryer).