There are a lot of great games out there using a variety of dice mechanics. Once upon a time, I wrote up how to use the Alternity dice mechanic in Risus. I wrote up using the Saga card-based system too.
I also have a soft spot for percentile-based system. D100 is just fun. Perhaps my favorite for that was Amazing Engine (especially the bit where you checked the one’s digit to see if you had a critical success or failure). I don’t know if it could be made to work with Risus or not, but I still like it.
Do you have a favorite dice mechanic?