This is fun to think about!

Colors - Reds, bright blues, mostly any bright colors! I love contrasts and interesting looking stuff. Chrome!

Colors - I don't really like pink or purple, so unless it's part of a pattern I rarely use them.

Thread - DMC, Anchor isn't too bad. I like the silky stuff since it's so smooth, and I LOVE metallic threads in spite of them being a pain in the butt to use. Shiny! I can't resist. I'm really interested in trying that Madeira stuff, but I haven't found it locally and am yet to order some.

Thread - Those off brands that break easily, run when wet, and don't really have numbers.

Fabric - 18 count Aida, evenweave, perforated paper or plastic (for ornaments and things).

Fabric - Low count (ie below 14) Aida.

Patterns - Dragons, Wolves, palm trees, natural scenes, outdoorsie themed stuff, fish, seaside scenes, boats, maps, rabbits, golden retrievers, most animals in general...

Patterns - Christian religious theme, sci-fi stuff, baby things, very cutesie projects (ie teddy bears, Disney...)

Kits - Kits are nice. I love small projects in a kit, since they are handy for traveling. Big ones are cool too, since everything is all together. Beads! I love stitching with beads!

Kits - Stamped. Stamped Cross stitch just doesn't get along with me all that well.
Things I would like to try:
Hardanger, some of the more fancy embroidery type stitches, really high count evenweave or linen, Madeira or other different varieties of floss, creating a 3-D project. I love experimenting with stuff.