A straight port of an M2 sniper arena.
A small arena with a central area and four semicircular additions, with walls to hide behind and windows to shoot through. Small enough, and with enough big weapons, that carnage rates should be absurd, even for two players.
A small, simple, wide-open level, with great flow and lots of weapons. Keep the total players under 4 or 5, and you should have seriously fast-paced killing going on. (More and you'd just get in each other's way...)
An extremely fast-paced map, with a tiny open arena in the center, surrounded by eight entrances on two layers... and a rolling staircase around the whole shebang. Absolutely no place to hide...
Sort of a takeoff of Everyone's Mortal... except with a shorter hill, and more easily predicted transporters. In longer games, fighting will narrow down to shotguns and missile launchers (no other weapons will have ammo). Getting around is really easy...