At the Horus Heresy Weekender there was an open game in the evening called 'Last Man Standing'. I missed it because it was late on and I wasn't staying at the hotel but I took a snap of the rules (see below). It's basically a death match between X number of players, each of whom takes control of a single basic Tactical Space Marine from one of the founding legions. They can be equipped with any of the optional s available to a tactical marine (including heavy/special but not sergeant only upgrades like plasma pistols).
The choice of legion is important because each one has a different effect on the basic stat line, for instance Death Guard get +1 Toughness whilst Space Wolves get +1 Attack. So think carefully about your style of play before you enter the arena!
The game was played on a sizeable Zone Mortalis set but you can just do one littered with cover if you want to. This looks like a great idea, provided that players are quick about it, there is also scope for other variants like, 3 lives per man, doubles match, king of the hill, oddball etc - I might thing of others as I go.
Anyways, have a game and let me know how it goes!
Death Guard, Word Bearers, Iron Hands +1 Toughness (Feel No Pain)
World Eaters, Space Wolves, Night Lords +1 Attack (Furious Charge)
Iron Warriors, Sons of Horus, Salamanders +1 Strength (Eternal Warrior)
Blood Angels, Emperor's Children, Dark Angels +1 Weapon Skill (Preferred Enemy)
Ultramarines, Thousand Sons, Imperial Fists +1 Ballistic Skill (Scout)
Raven Guard, White Scars,Alpha Legion +1 Initiative (Infiltrate)
Note: The USRs in brackets are my own addition to add a different dynamic to the game and I've tried to make it fluffy, take it or leave it! (IFIRC the logic behind the 'scout' group was more about tactical repositioning)
Whoever holds the Oddball has a thunder hammer (start of game have a roll off until there is a winner - they start with the 'ball'. If you kill the carrier, you get the ball. First to 15 kills wins! Respawns ON
King of the Hill:
Set up 6 zones around the board, these are labeled 1-6. Every turn you stand unopposed in the zone you score a point. Every 3-5 turns roll a D6, the 'hill' moves to that zone first person to 15 points. Respawns ON