I generally carry just the cheap ABC dry chemical ones because I can get them cheap/sometimes free from work, but for a car that I really care about I do have a Halon bottle.
What I would like to know is if any of the newer clean agent extinguishers are going to be approved by SCCA etc. any time soon, not that I actually race but I may want to do so in the future, Halon is expensive and is only going to get more so as time goes on...
nate