I had a small firecracker (about 1/4" in diameter and ~ 2" long) go off within 18" of my ear before. The fuse on the firecracker was bad and it just quickly flashed into the firecracker when I lit it. Good thing I wasn't holding it in my hand, I had placed it on the ground before I lit it.
Needless to say, my ear kept ringing for 2 hours after the incident.
On the other hand, a friend of mine had a similar firecracker go off in his hand while he was lighting it. It burned his fingertips.
I don't have access to that kind of laser but I have lit firecracker fuses and strike anywhere match heads before with sunlight and a magnifying glass.
Craig, do you still remember burning a peice of tape with a 50mw laser and a lens like that? You might already have a strong laser.