I would like to share a few tips and tricks to help you get that Gallium cross you have been eagerly eyeing for!
Ok here are the weapon combination that might kick ass if you use them right
1) Telsa gun with Chainsaw
Due to the stunning nature of the Telsa gun, you will be able to dispatch Zings quicker than a blink of an eye! Just remember to ZAP them first ok?
Combined with the Chainsaw's instant kill ability on regular Zings and the Telsa's anti friendly fire ability. You can pretty much run around killing Zings
without worrying about friendly fire. Make sure to use the Telsa for parasites. ( click to stun once, the switch into the chainsaw )
2) Flame thrower with Medi-gun
Playing as Faith, you pretty much transform into a badass flaming healing machine of death. Your increased healing ability allows you to heal teammates while conserving the irreplaceable ammo and your flamethrower makes quick work of Zing and Parasites. Just be careful not to ignite your teammates and conserve your flamethrower ammo. It runs out quickly
3) Auto-gun with Bullet Sentry-Gun
Playing as either Wildcat or Wolfe, you both deal massive amounts of damage if you play your cards right ( that is; don't spam too much ). Your Sentry gun will provide you and your team-mates with cover will you dispatch other Zings during crescendo events. Your Auto-Gun will assist in aiming for you and helps conserve ammo better than the Mini-Gun so that you need not reload that soon. Your Sentry gun is very powerful and can take on an entire horde by itself if you place it right. Just don't deploy your Sentry-gun too often or not it will run out of ammo and slow down your team. The beauty of this is that both weapons are available from the start
4) Prototype rifle with Pump-action shotgun
The Prototype rifle is another gun with the auto-aiming ability as well. It's stun grenades helps your team dispatch hordes of Zings in a jiffy. The Prototype rifle is a good weapon because it does not run out of ammo that easily. Your shot-gun helps you deal with near-by Zings which your rifle would not achieve as fast. Due to the high damage of the shot-gun, it is suitable for dealing with bigger creatures such as boomers, spawners, mortars and shieldbugs up close. Just make sure you do not waste your stun grenades before you need it
5) Marksman rifle with Telsa gun
This kind of loadout makes dispatching big creatures a whole lot easier. Your Telsa gun can help you deal with the average Zing and such but your Marksman rifle makes quick work of shield-bugs; provided that you are a good shot. You need not go as close to deal massive amount damage and with its moderate firing rate, you always have a second chance..
Miscellaneous items
1) Adrenaline: Super useful while trying for speed run achievements, its ability to slow-down time for your entire teams makes defending and hacking a whole lot easier
2) Electric Armor: Useful for the Mall map ( where you have to burn down eggs and bio-mass ). It allows you to detach parasites of yourself and deter any would be attackers. Just make sure you press 1, its not automatic
3) Damage Amplifier: Very useful while trying out for speed run achievements, combined with a chainsaw or two. Your team would be able to knock down doors in seconds. And with its ability to increase Sentry-gun damage, you can sit back and enjoy the show.
4) Heavy armor: Useful for general play, reduces all types of damage
5) Telsa coil: Super useful for crescendo events, you can instantly deploy Telsa coils and it does not run out that fast.
6) Blink pack: I do not know why in the world people would not pick this up at the last stage. The Blink pack allows you to TELEPORT anywhere ( that includes to your doom ) your cursor chance upon. You can use it as many times as you want but the recharge is long so make it count.