Sorry for the necro but I have been trying to catch up on the six month period where I was without an internet connection.

We have done sling duels here, in the style of pistol duels. Starting back to back with 3 tennis balls that have a slit in them to reduce kinetic energy. The "duelers" walk out to a predetermined number of paces and then turn and throw. If neither participant lands the first throw they are allowed to move a bit and try with the other tennis balls. Unfortunately most of these games end in a tie as the overall accuracy is on the low side. Fun none the less though.