where i play, they tend to get a lot of rental groups and children, so the surrender rule is always in effect in the woodsball fields. it is a 10' rule. within 10', you are not allowed to shot at each other. most of the bunkers are 8'x8' huts, so if you are inside or agains t the back of the bunker, you are within 10' of the other side. the attacker had to get to the bunker, bang on the wall and call out for the surrender. Surrender at this field is not an option, if you are within 10' and the other player calls it, you are out.
there are some questionable surrenders here and there, sometimes speedball players might "forget" and turn on you, etc... but for the most part, it works well.
my favorite way to surrender someone has got to be stepping away from the bunker when you know they are coming to tag it, then running back to it and tagging it myself. the refs know whats going on, but the other player usually ends up very confused and walking with a barrel bag on, lol.