How do you get them? Specifically the miniguns - couldn't find info online

Getting a certain score in endless mode, I believe

Just checked the rewards for endless, for future readers:

500 score - Double Shotgun 2000 score - Guitar 5000 score - Double Machine Gun 10000 score - Double Rocket Launcher

this is the normal mode too^

(accidentally got 7th on the leaderboard when going for this :P)