On my quest for the perfect pick for playing Black Metal, I've been through a lot of picks of all shapes and sizes. I managed to narrow it down to two picks in the end, Ultex Jazz III XL and the Flow 1.50. The Flow in my opinion has the edge (pun not intended), as they literally glide over the strings like no other pick that I've tried.
You might want to pick up a Flow Variety Pack to see which thickness suits you, personally I find anything above 2mm has too much "chirping" (at least when playing high gain) while anything below 1mm ceases to benefit from the aforementioned gliding at high speed tremolo picking. 1.50mm is the perfect middle ground, cannot recommend these enough and have already picked up a lifetime supply. The quest for the perfect pick is finally over.
Or is it...