Hey there, I just did a simple but useful lightbeam sprite for my project. Since I think it can be a very handy asset and because I'm a rather generous person, I've decided to give it away to spare you a bit of time.
It forms a straight yet cone-shaped beam, it may be pretty difficult to see it in bright areas, so my advice would be to place it in the dark ones. It gives a very nice effect when placed under a hanging ceiling light or a grating on the ceiling ( like on my screencap ).
Also, they seem to be really big on my screenshot : that's because I've set their scale to ~300. I gave to them the same properties than the Simon Benge's "flareblue16" sprite ( except for the scale, of course ).
Enjoy ( DL attached )
"I like to keep this handy, for close encounters."