I've been told by a fisherman that its a male sand flea (aka mole crab) but cannot verify it. I've often been pinched by them while digging for fleas with my hands. They have pinchers.
OK SWGB, that thing is called a....drumroll.......sand crab!
[ame=http://en.wikipedia.org/wiki/Hippoidea]Hippoidea - Wikipedia, the free encyclopedia[/ame]
Also called a Spiny Mole Crab. A different species than what is known as a sand flea that everyone who knows fishing the surf uses for bait.
I used to think they were male sand fleas, but they are not. I still use them for bait even though they are IMO much scarier looking than sand fleas. I can actually say I think they do not work as well as sand fleas. I think fish are afraid to eat them.
I too did the wikipedia thing and found out male sand fleas are merely a smaller version of the females.