lol for last campaign, had a sniper, a dual machine gun and 3 damage buffs. the machine gun was doing 7 damage a shot, and the sniper 73 with fully upgraded fire rate :P was the easiest campaign for me
here's for a fun strategy:
after you've gotten some money with dual machine gun, sell it and buy only homing missile launchers. only upgrade reload time and in battle, just keep the rockets in the air until something comes. sometimes you'll have like 20-30 rockets waiting :D of course, this only really works when there's big ships, when there's a ton of small ones it sucks
paletti:
just find a pretty big open spot and try to go around in circles, i got a skid of 300 :)
and chozo:
lol, try to enjoy a challenge, the game is really not that hard. for level 6, you have to hit a lot of the barrier things