I'm hoping I'm posting this in the right section and I'm also hoping this is an easy question to you all veterans!
As far as I know, you are forced to get certain weapons in certain missions to progress it.
I'll list all of what I remember, tested and watched:
~ Ken Rosenberg - Back Alley Brawl: You automatically get a Pistol replacing any weapon you had before, like the Colt Python which is better... (Previously tested by myself).
~ Juan Cortez - Treacherous Swine: You automatically get a Chainsaw and it replaces the previous weapon in that slot, at least this is the best weapon of its type (Previously tested by myself).
~ Juan Cortez - Guardian Angels: You must obtain the Kruger/Ruger replacing any previous weapon like the M4, this only for Lance Vance to come to progress the mission (According to my memory).
~ Ricardo Diaz - Phnom Penh '86: You automatically get a M60 to kill the sharks gang from a Helicopter. (According to my memory though I'm 100% sure).
~ Auntie Poulet - Dirty Lickin's: You automatically get the Sniper Rifle replacing any previous weapon like the .308 Sniper (aka PSG-1) (According to my memory).
~ Malibu Club - The Shootist: Asset Mission. You automatically obtain a Pistol always replacing previous weapons. The unlocked Side Mission "Shooting Range" is the same case. (According to my memory though I'm 100% sure!).
~ Phil Cassidy - Gun Runner: You MUST obtain a Colt Python, SPAS Shotgun, M60, and a Mac forcing you to replace any previous weapons. (I didn't remember about this one but I watched a video and it looks like you have to get the weapons no matter what!)
Any other mission to talk about? I really need all of your help! This is a huge research to do alone. >.<
Videos do not show the enough info behind what really can happen...
I need this info to keep certain rampages in a starter save. (<cough> do not ask why <cough> <cough> hehe I'll respond anyways)
Did I just mention it all?