I always use:
WA2000
Spas
Marathon
Stopping Power
Steady Aim
Claymore
Sniping definitely isn't for everyone, though.
Tips for sniping:
-Don't travel with your team. Flank, flank, flank.
-When turning corners, switch to your secondary. Once you become familiarized with sniping you might be able to start no-scoping, but make the secondary a habit.
-Once you get a kill, move after a few seconds. Unless you're content with camping, like a another guy said, people like to get revenge. Staying in one spot is fine, but you'll get a lot better at quick-scoping and learn to take better routes if you're on the move every once in a while.
-Pick spots that will provide you with opportunity. Not every map is great for sniping, but most of them have at least 3 spots that are suitable for sniping.
-When you miss, don't rapidly fire hoping to hit the dude. Instead, get out of the scope view and then instantly go back in. It's a little faster than waiting for the recoil to subside, and it'll make you better at quick-scoping.
-Learn your enemies' habits. This goes mostly for clan play, or just playing with friends on a regular basis. Humans are creatures of habit. People typically like to go to a few places on each map and will stay there. You can pick up on the habits of an enemy in a single match, and exploit those in the next.
-Use your nades as tools to flank with.