There used to be a green one in the astronomy department at school that was used as a star pointer. The advantage was that you could see the full beam extending up, whereas the red you couldn't unless it was slightly misty, in which case nobody would be doing astronomy anyway.
Looking on eBay I'm suprised how cheap they are. To be honest I never considered the effect they'd have on aircraft at the time either.
There's also another website that advertise both red and green lasers as a kind of survival flare. The beam is an elongated ellipse (almost a line) rather than a normal pointer (a very narrow conical beam) to 'fan' the surroundings. I can't say I'd like to have any one of them shone in my eyes while flying at night!