I bought an Olight M20 from Airsoftparts and I love it. It has 4 modes: low, med, high and strobe. Comes with some extras that were neat. There are also filter, rail and and pressure switch accessories available. I have yet to be shot in the lense/bulb area, so I can't tell you if it is durable enough to take it.
It's around the $100 mark (not including accessories). IMO it is overkill for airsoft (320 lumens on the highest setting), but I appreciate a good light, and I don't regret buying it.
http://www.airsoftparts.ca/store2/in...oducts_id=1799