Uhh... Bordertown? That's not a terribly good idea.
A good 1v1 sniper map is Kosovo Night, especially when you both spawn on opposite sides of the river. My brother and I played that quite a few times, and it led to some rather tense matches. The map also works for one on many.
Another good, smaller, 1v1 map is Chiller. Sublime and I used to play that one quite a bit. I have yet to shoot him out of the damned frozen pool in front of the house, no matter how many times I've tried.
And to toot my own horn, I may suggest Bunkers. It's a copy of the Rogue Spear level which provides some really intense and quick 1v1 matches. The map is really simple so you'll learn it very quickly, but it has a lot of strategy with a small number of players. Play this one on DM, not TDM, though, to make sure that you spawn all over the map. I've seriously put more time in on this map on private LANs against one other person than any other map (between Rogue Spear and my Inf copy).
Hope this was slightly helpful.
-tc