Well, let's continue about a tutorial in how to select the best weapon for the current job.
- Dretch => anything works but Mass Driver and Lucifer really shine here. Shootgun is good too.
- Marauder => very obvious : the shootgun is the perfect Marauder killing weapon. Lucifer works too with some skill
- Dragoon => ChainGun is in my opinion the best weapon to kill a dragoon. It's good at close range and very good to kill a fleeing dragoon. Since all dragoon you'll face will be either chomping your head or fleeing in terror, that's the best weapon. In the case of a particularly bold dragoon who never flees, Lucifer if better though

- Tyrant => see dragoon.
Now, those are the best weapons to kill aliens in my opinion, but killing aliens isn't the only thing you need to do. And it's not like all fights will be some kind of 1vs1 where you know all about your oponent. You also have to kill alien buildings. For that, you need at least the armor or else acid tubes will eat your health very quickly.
The building killing weapons are :
- painsaw
- pulse rifle
- lucifer
Buildings have lots of HP and so will use a lot of ammo to kill. Also, you want accurate weapons for when you need to snipe a far away building. And last, since most of the time you'll be in the middle of the alien base to kill the buildings, the faster you do it the better. Of course, painsaw can only be used against ground buildings and only if there is no pesky trapper on the way. If there is no acid tubes around, you can also kill eggs on the ceiling with painsaw + jetpack.
In my opinion, except for the lasgun and the flamer, all other weapons are horrible at killing buildings.
So, let's see now the second best weapons for the job of killing aliens. That way, when the oponents have mixed aliens and you have to go alone, you can better chose a weapon that can be used against a large range of oponents

- dretch : machinegun, lasgun, pulse rifle ( close range only )
- marauder : chaingun, pulse rifle ( against agressive marauders only )
- dragoon/tyrant : shotgun, pusle ( close range only, long range for suppresive fire )
So, what do we learn about that ?
At stage 1, there isn't a good weapon that can be used both to kill a base and to kill aliens. Teamplay or painsaw rush is required at that point if you want to kill the alien base. Also, weapon choice has to be very careful depending on the state of the alien players. If most of them are still dretches of basilisks, use the massdriver if you can handle it, or else use lasgun or shotgun. If there are quite a few dragoons around, use chaingun. If the dragoons are good players, you will need teamplay and go at 3vs1.
At stage 2, the best all around weapon is the pulse rifle. It can be used efficiently to kill any alien and to kill a few buildings on the way. Most annoying are dretches who do not get in close range and marauders which can avoid easily the pulse fire.
At stage 3, lucifer is better in my opinion because it's devastating to dretches on the way ( to the alien base

), can cripple an alien base in no time ( you only need 1 fully charged shot + one least charged shot to kill an egg for example ) and can be used to scare away the bigger aliens too. Chaingun only works against bigger aliens and is a pain to use against dretches.
Note :
- painsaw can be used to destroy any alien but it needs good skills to do, and it only works in defensive ambush situations agaisnt good players
- I still have difficulties understanding what happens when I use the flamethrower. Not that I can't kill with it but that weapon feels weird and unreliable for me so no mention of it either. Although it is a viable base killer I must say.
- Basilisk isn't mentioned either because I do not have enouth data on that one

Anyway, it feels like any weapon is good enouth to kill a Basilisk with the lucifer beeing by far the best in that case : a lucifer jump will not only get you out of it's grasp, it might also kill the basilisk in the process.