I've had a lot of fun with this one. When you shoot barrels to half damage, they begin to burn, then explode a few seconds later (like HL2 barrels). When barrels clustered together, it causes a very cool chain reaction: When barrel explodes, it causes nearby barrels to burn/explode, etc.
You also pass in an array of soldier groups that you want to burn if the unit is within 10 meters of an exploding barrel. I realize it would be cleaner to just find any unit within 10 meters of an exploding barrel, but that was a bit too complicated for me...
Any feedback would be welcome. Especially how to make this work better for multi-player (the barrles explode on all clients, but not all players can see the fires?).
Unzip the attached file to your User Missions directory, and then run it via Mission Editor Preview.
P.S. Credit goes to GeneralBarron for his fireEffect.sqs script. I use that one alot!