I carry a drain blaster, 2 steamers (incase one breaks during a job which happened before to me and had finish job with my backup hairdryer which takes forever), and several small snakes. I use Shark steamers with a hold down latch, makes job easier on you thumb. For some of the big, old GE evaporators, I hook up both steamers and use 2 hands to make the job go faster. I can snake out some dishwasher hoses without removing dishwasher and this is good. Steamer is best tool to clear a plugged drain tube for my purposes. I rarely use the CO2 drainblaster, but I did buy it when it first came out. Potential for damaging tube is too great in my opinion.
I also carry a small Air compressor and can use that if I need a shot of compressed air, or for cleaning coils, etc. I have a small needle-nose gun I got from Harbor Freight that works perfect on a lot of jobs, especially blowing lint out of motors.