For those who don't know, the Light Gun was a peripheral in the form of a gun, which one would shoot targets at the screen. The term 'light gun' came from the gun using tricks of the light to determine whether the target on screen was hit or not.
Examples include the almighty Time Crisis, the Immortal House of the Dead, Ghoul Panic, Point Blank and the classic Duck Hunt! What's your favourite series?
The classic Duck Hunt. I was never sure of how it worked when i was a kid, but I didn't care. Of course, over time, we all learn. But, even today, I'd pick Duck Hunt over many modern shooters. For me, it was simple, and easy to jump into.
House of the Dead was always my favorite. My brother and I played the heck out of the one on the original Xbox (HotD 3, though it also came with HotD 2 as an unlockable). I keep hoping that they'll come out with a compilation disc that includes all of them (1-4), but so far I haven't seen it.