FLX and Elite X. I don't have a lot of discs in X, but I think I'll grab a few before winter gets here. Always something really bright too. When the discs hit in a hole or divit that would normally hide the disc, you can actually find them by the reflection they cast.
I throw the same stuff in the summer and winter. Z plastic and esp. Keep enough handwarmers in your pockets and put the disc in your shirt with your throwing hand holding the disc where you want to grip... feels like summer grip...lol
i like flx the best in the winter but i find that star is decent as well. also a nice little trick i learned is that if you let your discs get cold before you start to play it makes it easier to play because the snow will just fall right off and wont melt on your warm disc and then freeze causing ice on your discs. and it saves alot of time because you dont have to wipe your discs off after every throw. i usually will just leave my discs in my trunk or garage to keep them cold.