Do people really have favorite sets of dice? I certainly don't, though I have a soft spot for a particular d20 that always seems to roll well. But my favorite die is an orange spherical d6 I picked up a while ago. It's a sphere, but inside there is a set of grooves and a ball bearing, such that it will come to rest on a number just like a cubic die. It's not really practical in play, but I think it's pretty neat.