GOB Scopeshot

It's available in Deathmatch and Team Deathmatch, the best gametypes for sniping wars, naturally. :P I still think you could probably play these so-called sniper maps with a full array of players, though, so why not give it a try? Check out the screenshots of Scopeshot below, and download it now! ;)
Here's a brand new sniper map of sorts by JackC, which he appropriately calls "Scopeshot." The map is simple and features two ends separated by an open section and scattered debris in the middle.