I know that of all people I shouldn't be offering information, but what the heck, right?
Give a bolt-action rifle a try. Although if you are a trigger happy kind of person, you may find yourself in the position to buy a full-auto airsoft rifle. An M14 would be fairly great because (not sure of this 100%) most, if not all of the M14 airsoft rifles are semi-automatic. I am sure there are some that are fully automatic aswell.
You can also go out to games and ask to fire some peoples airsoft rifles to get a feel of what you like. Most of them, from what I have heard, will gladly let you pop off a few rounds.
Whatever you find yourself buying I am sure you will be happy with. Just remember that airsoft sniper rifles are next to nothing like a real sniper rifle. Their range and accuracy depends on the shooter, and the ammount of money put into the rifle. Chances are if you buy a stock weapon, the cost to upgrade it to something that is worthy of field use. You will be looking at up to or over $1000.00 to upgrade it to make it work well for you in the field.
And like Drake said, the sniper role is about a very specific skill set, not about the rifle.
Yesterday's tears are today's wounds
Today's wounds are tomorrows scars
Tomorrows scars are your life's war cry...
-Fuck 'em up Gentlemen