Best way to "counter-snipe" would be to learn as much about "sniping" as possible.
The reasoning being that the more you know, the more you can look out for and "think" like the guy who's stalking your team, and the more likely you can be pro-active (or at least effectively reactive) against their techniques.
I was given the impression that sniping has alot to do with tactics before it even comes down to the gun you use, so it seems sensible to work on the techniques before deciding on a gun.
Torn: Your story reminds me of a short skirmish I had at the field near my house - I didn't get stepped on, but very close, and I almost gave one of the players here a poke in the thigh with my Benelli and whispered mercy. He was kindof in shock about it, so he didn't say anything, and while the guy behind him was trying to figure out what was going on, he got 3 in the chest 8) .
Ah yea - and Saint - I don't think people hate being sniped as much as people hate being sniped by someone running full-steam-ahead. A big, huge rifle isn't a damned assault weapon.