Hero

This battle pits a few hard-to-kill people against the entire rest of the field. It can be good training to teach people to be aggressive and mobile.

Regen: None, though Heroes are very hard to kill (see below)
Teams: Heroes versus everyone else. Heroes should be horribly outnumbered, perhaps 7-10:1. The ratio of heroes to everyone else and the number of hits a hero can take can be adjusted as appropriate.
Rules: Heroes do not count their own armor, and their sheilds cannot be broken. Heroes do not die as normal and they never lose limbs - instead they keep a running count (out loud) of how many hits they've received regardless of type or location (a single green to the leg counts the same as a red to the chest). Once they've reached a predetermined number (10-20, normally), they die. Normal people die, lose limbs, count armor, and have their sheilds broken normally.
Tactics: Heroes must keep running, constantly, and must win through attrition. Heroes normally die by becoming trapped, surrounded, falling, etc.