Free rules, tactical, official GW Warhammer game that you only need 1-5 models to play. Pit Fighter.
I had no idea about this, found it by accident. More people should know, I'd start playing this right now, with $10 spent on eBay if someone's in San Diego.
1. Free download rules at http://www.games-workshop.com/MEDIA_CustomProductCatalog/m1340002_Pit_Fighter.pdf
2. Official arena map: http://www.games-workshop.com/MEDIA_CustomProductCatalog/m1340003_Pit_Fighter_Boards.pdf (or use any medium-size hex surface).
4. http://tabletopgeeks.com/wp-content/downloads/supplements/TownCryer14.pdf Campaign rules.
3. http://tabletopgeeks.com/wp-content/downloads/supplements/TownCryer21.pdf Warbands expanded.
Rules available for:
Chaos Pit Fighter
Empire Pit Fighter
Orc (with "Waaagh!" special move)
Skink (javelin & net)
Witch Elf (forward/backward flips)