I got my first during the last mission of my first playthrough. Second playthrough and I haven't gotten an alien weapon in the first 3 missions, but I have replaced almost every weapon I was using already...
Eridian weapons are reandom drops^^. There are a total of 7 different weapons (for every normal weapon type one). The effects they have are always the same, but the effects are hidden as the names and description only say stuf like 1010010011010101. You can look into the borderlands wiki if you want to know the special abilitys the different guns have.
The lowest one I found was für level 18, the best one for level 42. When you know which special abilitys they have they can realy rock^^. They neither need ammo nor there are weak ones. And the reloadrates of the energy can be easily increased by getting some skill in it. I have my eridian weapons skill on 90 now and the the rocketlauncher version of the eridian weapons nearly reloads as fast as I can shoot^^. On top of that they RELOAD WHILE YOU USE OTHER WEAPONS. I have 4 eridian weapons and I always switch between them so I NEVER run out of bullets
But as I said, you need a skilllevel above 40 OR more than one gun to make them useful. only one of them is useless as the reload times are just too high^^. Oh yeah, don't look at the damage the weapon does in theory. In real every weapon has bonus dmg effects like electro dmg over time, doubled crit dmg and stuf, but you have to test the weapons to find out. As I said, you never see what they can do from the description^^.
(before you ask, I had the lowlevel version of the eridian blaster and I now have ereidian rocketlauncher, shotgun - also called thundergun, sniper - which shoots bolts which hit the enemy INSTANTLY --> NO TRAVELING TIME --> perfect for good 600 meter away kill snipers^^ and the mg type which shoots wierd bullets which can stun the enemy)
Simple. Use the item duplication trick with him. You host a MP game, he joins, go to an area away from a New-U device, have him drop what you want (Since you're away from the new-u device his inventory changes won't be saved), and have him exit the game right after he drops what you need. You pick them up and head to a new-u device and you're set.
My name is Everfades. The only thing I realy cheated are my skill points^^. Everything other is hard played .
But there is a crate which has 8% chance on dropping an alienweapon for level 19. The only one I know with a that high chance (given from the data of the game!). It's in New Haven on one of the roofs. It's the one which drops ammonition (red colour crate), too, and which has another of the small crates which "only" spawns weapons but no ammo (those grey ones).
So just log in, farm the crates (there are a total of 4 just in the city itself) or only the one with a high alienweapon dropchance (dropchances AREN'T random for all crates, some like the described one have higher chances on rare weapons!). You can for sure search in all crates as there is ALWAYS a possibility of getting an alienweapon out of them. So log in in New Haven, go and loot everything, relogin, all crates are filled again. With only one hour work you should at least have 3-4 alien weapons and 5-10 yellow up to orange ones and if your are REALY lucky a diamant one^^. (they have awsome text effects, for example the for motherland text means 5 times more grenade damage which is AWSOME for healing grenades).
Enjoy the search, it's more fun not to cheat in a game like this . Lucky finding to you and have fun playing^^.
EDIT: Sorry, I meant 6% chance.
[Edited by Everfades, 10/30/2009 2:29:03 AM]
All times are (GMT -08:00) Pacific Time (US & Canada). Current time is 4:30:53 PM