Ditching
A popular game in Belegarth which was adopted from Amtgard because of its simplicity and self-balancing. Two teams fight, first dead on the winning team switches to the other team.
Setup: split fighters into two teams. This is normally evenly balanced, but any system is fine (vets vs newbs, polearms vs shields, cake vs pie, whatever theme you like at the moment). Start game.
Rules: the first dead of the winning team switches to the other team. This way the game auto-balances teams. If new players come onto the field, the losing team gets them instead of first dead of the winning team. (If a team fails to kill someone on the other team, no new fighter for them.)
Alternatives: a team must lose X number of times (often 2) in a row before they gain a new player.
Goal: kill everyone on the other team. Reset, start a new round. Ditching is a self-balancing game, so there is no way to "win" ditching overall: rounds continue until the next water-break/game change/end of day.
Known issues: if archery is being used, the archer will virtually never switch teams. (This isn't an issue, but is noteworthy when setting starting teams, or new players coming into the field.
Note: in Amtgard ditching, missile weapons, armor, and what they consider class abilities (ie: shield breaking) aren't allowed, so if you have crossgamers make sure they know Belegarth ditching uses full Belegarth rules.