D4 for me, the caltrop of the dice world.
I love the D7!But I love the D12 more. It's perfect.
Much love for the d30 here. Running a close second is the d6 -- the workhorse of the gaming scene.
I am enslaved to the d10!
I'll have to say d10.
Said it before, say it again, the d12 is a thing of unique elegance.
You have great taste in dice. This is my favorite as well.
The d6. It's got it all: it's traditional, it has a good range of results without having too many, it's the basis of some of the best bell-curve rolls (2d6 and 3d6), it can be found anywhere (not just in hobby shops), it's the basis of pre-Greyhawk D&D hit dice and damage rolls, and it rolls well without rolling off the table. Second place goes to the d10, for its decimal value.Least favorite is probably the "Zocchihedron" d100, the most pointless die ever made.
I don't even _own_ a d30, but my lust for it is so intense it may just be my favorite. Outside that realm, I think it's probably the simple d20. It rolls really, really smoothly; I've got a clear idea which ones are high and low rollers since I use them so often; it's practically the symbol of our hobby.
I'm fond of the boxy d24, probably second is the d12. I've often thought of creating a series of Duodecimal houserules to use two d12's in place of 2 d10's. Though so far I haven't found any dice labeled in Duodecimal.
d12. Hell I created two games that use them.
The D30, hands down. I was so enamored with this cool new die I modified my homebrew to utilize it! I can still remember the look on my playing groups' faces when I slung that bad boy on the table the first time... :-)