Types of grenade launchers etc

Okay, this post is gonna be about grenade launchers...
I don't mean different styles or designs, since I know there's a ton (like rifle-mounted launchers, 6 barrel pump action launchers...) but I mean function. What different types of grenade launchers are there? The only kind i know of are the kind that shoot the spray of BBs out of a canister. I've heard of a kind that launches the canister out, which then explodes with BBs after it's launched. Is that true? Also, is there any sort that can be attached to a gun without a rail system? I sort of want one for my AK47, but i don't know how I could get an RIS for an AK.

you just buy a rail seperately.
http://www.airsoftpost.com/rail-interface-system-ak47-series-airsoft-p-28785.html

and pluck on a M203 on it.
There is one special M203 I've seen in SC Village, a guy had a m203, on the side, and it was connected to vertical Grip.
I think i saw it at evike, not sure. But it helped him alot!
other then that, you can get just those classic M203s.
If i were you, buy a M203 compatible for Ak47s, the ones for m16s, are too long. FOR EXAMPLE.

http://www.airsoftgi.com/product_info.php?cPath=139_128&products_id=2005

maybe this one?

http://www.airsoftpost.com/jungle-series-m203-launcher-military-type-short-p-24884.

thats all i have, I SHALL KEEP LOOKING!

or you could get a mosqito (I know I didn't spell that right) compact grenade launcher for an ak. It would look great.