What fire extinguisher

As my title states, what fire extinguisher would be best for me to have when i'm out bashing?

may seem like a stupig question, but if something does go spectacularly wrong i would like to be able to bring it back under control quickly... so fire extinguisher it is :P

would a foam or CO2 one be better than a water one? as if i loose one of my components i would still like to be able to use the rest...

does anyone carry a fire extinguisher with them on bash days/have one in the car just in case?