Okay, maybe that's an exaggeration, but it still made a big difference in my playing! This is the Fred Kelley bumble bee teardrop pick, and it was recommended to me (indirectly, alas) by none other than Steve Earle. (A friend ran into Steve at Matt Umanov's in NYC, and they chatted a bit--during which time he recommended this pick:
The beauty of it is that it acts as a thumb pick and a flatpick. You can move instantaneously from flat picking to finger picking.