Heh, title of your thread made me laugh, so here's a link for you at least
**broken link removed**
No, none of them are specifically for zapping your neighbours, you would presumably have to adapt whatever circuit you find to suit your requirements. The ones using phototransistors as sensors are probably your best bet, I think LDRs are becoming a bit uncommon nowadays?
I think it would
probably be a good idea, if you've never done any electronics before, to start very simple and try just building a circuit that turns an LED on and off (like most of those on that page) depending on whether the laser etc is shining on the sensor, and THEN when you've got that much working, see about how to connect that with your uh... toy gun thing?
Or whatever it was you wanted to use...
I'd think the easiest way to activate the gun would be a relay or similar in place of the switch on the trigger, but I've no idea how the thing is made so I don't really know. Anyway, that's the extent of my suggestions, so good luck
(Hmm, and also I suppose Arun's point about lasers being a bit dangerous is true, they can badly damage your eyes or even blind you, even if they're infra-red ones!
)