juice and Andi have tried to make some of levels on alien harder by - adding few rubbish gun so you cant use the best ones BUT, my fav gun on game is Frozen Death and its only playable on campaigh! why! and the level is simply IMPOSSIBLE!! ( i bet a million some one will come here and say "i did it"
It takes two shots to take out the raze soldier with the holy grail. It only takes one shot to take out Johny Rocket even though he has adrenaline boost it just burns out the last hit point.
What's up with the Holy Grail? I personaly tested it, and I don't like it. It only has one bullet per mag, so if you miss, you have to reload. I beated this level with the Pulsator and I didn't used it at all. Since you spawn with the Explosive weapon, use it. If you noticed, it has more bullets per mag and more mags esecially on that level, so use it as your advantage.
To beat levels, you need skillz and luck. Weapons don't matter, at least not so much as the way you use them. People beat levels and use different weapons.