My dad's cat doesn't seem to react under 300 lumens with a constant light, but he does close his eyes and turn his head around when shining a TK45 on turbo at him. I can't remember trying the strobe.
My cousin likes to try to blind his neighbourh's cat, but has had very little success. I don't approve, but he hit him with a 50mW green laser with some success.
I once had a strobe party -many many years ago- and my Cocker Spaniel retreated to the basement within a minute. I do have to add we were pretty drunk and acted like idiots doing the robot. I suspect our behavior and the loud music had something to do with it.