I always use Wegen picks for mandolin. Made by Michel Wegen in Holland out of aircraft-grade plastic. Pre-bevelled (you have to specify left or right-hand!)last roughly forever. Lots of gauges, but I use either the 1.5mm or 2mm picks for mandolin. He also makes an asymetric triangle called the Dipper, with round, semi-round and pointed corners; a different tone is available from each corner. You can get them from http://www.hotclub.co.uk/shop/acatalog/index.html
No financial interest, just great picks.
Tim