Height
Weight
What type of water you paddle (and class)
Favorite boats
If you could only own one boat...what would it be...
For instance:
I'm 5'9"
About 155 usually
I paddle what most consider "bigger" water, like the Hudson gorge, Kennebec, but also enjoy rivers like the Schroon, Salmon, Sacandaga, James, and even REALLY BIG water like the ottawa. The Potomac is fun too (I've only run the NB and little falls). I like running class II and III in squirt boats, but am confortable in class IV, and occasionlly in V (Bottom Moose).
I enjoy squirtboating the most, usually in my Master Cut Acrobat, Standard cut acrobat (a bit more speed), of if I'm really trying for DT the Maven (and, hopefully next year the Mentor:) ). Part of my reason for squirt boating is it gives you the ability to "take the river up a class" if you wish, and most of my friends are class III paddlers (not to mention that is what is closest to me, other then steep creeks).
For bigger water I really like my Viper. Fast, and very stable. I've just purchased a Sith, and anxiously await it's arrival. I suspect it will become one of my more used boats, as it does a lot of what I like to do well (stern or bow squirt, surf), and is exceptionally comfortable and stable. I also like my Fanatic II slalom boat for bigger water (not to mention gates:) ).
Right now, if I could only own one boat (and not having paddled a finished Mentor yet), it would be a Sith.

As some of you know, I'm "north country frugal" (aka CHEAP), and typically purchase used boats. Of the 29 or so boats I have right now, 4 (soon to be 5) were purchased new. So a boat has to be VERY, VERY good (the Sith) for me to purchase one new:)
For the curious, the other new boats:
Atom - sold my Cascade and Slasher to buy one...only CBoating a few years at that point, and no clue what else was out there. At least I got a 'VIP' deal on it

Groove - THE hot boat at the time...and a far better boat than I was paddler (still is, too). Fun though!
Tomcat (yes, a ducky) - for AdkSara and i to paddle together
Wheelboy - truly a great boat, especially for rodeo type paddlers. After paddling it a bit, I decided I really do prefer longer, slicy boats. Just a personal preference!