If you just asked “what the heck is an ROUS?” then you must immediately watch The Princess Bride, the most quotable movie of all time.
You can cheat by going here:
ROUS overview
and see one here:
and
But truly, go watch the movie. It will not make you feel dead all day, but it will make you realize that you are using the same wind that I am using. And don’t even get me going on how it’ll change your life view on rhyming.
Anyway…I would likely use my CMR-30. The .22M, even if it took more than one shot (they’re slow) would get the job done and it is fun to shoot, adding to the feeling of satisfaction. Plus, the large capacity mags are light and easy to carry. A flamethrower is just too hard to carry, but I wonder if some sort of grenade or maybe just a basic 9mm would be a better backup.