I'm unable to program (read: too lazy), but I think that the ability to "spoof" enemy weapons with a push of the SHIFT button would be a cool idea.
Basically, what I'm saying is that something that significantly reduces the range of an enemy's light gun tracking temporarily would be cool, while not being as all-encompassing or overused as a cloaking device or something along those lines. They'd still be able to see you, and would be able to open fire, but their light guns could only fire straight ahead.