You might want to throw a utility knife and some replacement blades in the glove box since cutting hoses and mounts is a blade destroying task. That way you can replace the cheap utility "razor" blades as they get dull.
Another good option for a vehicle kit is a small folding saw. You'd be amazed how useful a little openel camp saw is for cutting up tires, hoses, etc. Gerber, Openel, or even the saw on a large SAK are great.
The Airforce Survival knife from Camillus is great and serves well as a general duty knife.
For a chopper I'd get a BKT Brute or one of John Shirley's favorites a HI Kukri.
Keep in mind that you can get all of this for less than the $150 you're willing to spend and have tools tuned to do the jobs you might encounter and without taking up much more room than a single big knife that won't do any of the jobs as well.