My favorite is Panic, but witness is cool too because it doesnt use anything that you need to use as a gimmick that you could possiby lose. I've had Distortion, but the gimmick broke because I played with it before I watched the dvd. Distortion was pretty cool but the gimmick is scry cuz its easy to break. I think I know how Digital dissolve basically works and some of my friends have it. It looks really great. The trilogy dvds are really great. I only have the tricks dvd, but its got a lot of really great hardhitting effects that can be done surrounded with a borrowed deck of cards.
I would recommend you get at least one of the trilogy dvds because it comes with more than just one effect but if you want to get a single effect off t11, then get Witness if you want one that can be done without hard to get materials. If you want a gimmicked trick, get Panic because its really really easy and hard hitting.