Spoilers ahead.
After playing for a few hours, I've been looking at various walkthroughs at No Mutants Allowed. I wanted to see what I've missed in the early game and get more info on character building. They mention two things in Vault 15 that I haven't been able to find in my game.
There's supposed to be a hunting rifle hidden in a bathroom on level 2, but I can't find it. I thought it would be neat to get this since I created a Sniper-type character.
Also, there's supposed to be a message about the water chip & 500 xp triggered by walking near the collapsed door on level 3. I don't think I've gotten this message, but I did get a message about emergency supplies being buried under rubble in the meeting room.
Has anyone been able to find the hunting rifle in the GOG version of Fallout 1? Does anyone know if the GOG version of Fallout 1 has some changes from the version used by the creators of the walkthroughs?
EDIT: I just read a walkthrough that mentions the water chip message, but not the hunting rifle...

Err, you are in Vault 15 right? Because if you are in Vault 15 level 3, then you should get it. I got it.

I may have gotten the message but scrolled it out of the way too quickly by pointing at a bunch of other stuff. I will probably try to reload and watch more carefully this time.
My current character has a perception of 8, so I think that's high enough.
What about the hunting rifle? So far 3 out of 5 walkthroughs have mentioned it. Maybe it's random or luck based? Or based on a skill?

I don't think I ever found a hunting rifle in vault 15 and I owned the original and have about 100 replays. Are you sure they aren't confusing the SMG with a hunting rifle? Only items I've ever received on level 2 are the lether jacket, a rope and the ammo clip.

On my third walkthrough, I was careful to pay attention when I was in southeast corner, and I finally saw the message.
The first two times I must have been too busy shooting rats or blowing myself up with dynamite to notice the message. On my first walkthrough I was fixated on trying to use the dynamite to clear the room, but that doesn't work.
The SMG is in one of the lockers, but the Hunting Rifle is listed as being in one of the bathrooms. 3 out of 5 walkthroughs specifically mention a hunting rifle in a bathroom. But I never found it.
But I'm over it now, because I was able to acquire a hunting rifle and a truckload of .223 ammo in Junktown.
Thanks to everyone who posted.

Items on the ground are almost impossible to spot in this game, very annoying. The low resolution can be annoying at times, and even using the high-resolution patch doesn't help much since everything just gets smaller.
However, I was able to find the hunting rifle myself, it's all the way in the very southwest room in the bathroom, just lying on the floor. Looks like a little brown toothpick lying there.

Yarg!
I spent a few minutes "mousing around" in that stupid bathroom and never got any indication that there was a moveable object in there. Nothing but "You see a Wall" "The last guy didn't flush"
I was able to find ammo and a crowbar on the floor, but the stupid rifle appears to have permanently escaped me.
Oh well, not a big deal. Got my rifle in Junktown.

My perception was only 4 and I found the rifle.
A big problem is that you have to walk right on top of walls to make things visual. You can't click from the middle of the room at a far wall, or even from the side of a room. You have to walk the character itself to the end of the area to reveal everything in it when you have blocking walls. Do that, and click around, and you will find the hunting rifle. If I can do it with perception at 4, so can you.

I think I might have killed a rat that died on top of the rifle, making it hard to pick up.

Well, i bought Fallout GoG version today, and i found the rifle, after i followed a walkthrough.
Its in the sw corner rooms bathroom in vault 15, level 2.
Its up in the NW corner of the bathroom, have to walk all the way up in the corner for the floor to be visible, and you can see it, but its HARD to spot.
And im fairly sure i never got it in any of my earlier playthoughs of Fallout. It made the raiders camp VERY easy.

the rifle IS there, but it is REALLY-REALLY hard to spot. gotta be an expert pixel-hunter to get this one. the rat might have died over it also, covering it with its messy intestines, and making it impossible to spot.
btw, standing in very corner of that bathroom might help noticing.

Okay, I hate myself for asking this riduculous question, but whatever, here goes.
Do you need to be standing to the left of the toilet (near the "top" wall) or is it better to be standing near the bottom wall near the entrance, or maybe right near the toilet?
I figure you have to be in a position that the wall covering the item becomes clear, but you can't be standing right on top of it or you can't highlight it. Does that sound right?
It doesn't really matter for my current walkthrough, because I've already got a sniper rifle, a combat shotgun (whee, full auto death!) and a plasma pistol. The .223 pistol is great and all, but I was like "meh" and gave it to Ian. Now he kicks a$$ in combat. Except when he decides to go melee, the idiot. I had to take away all his melee toys, but he will still occsionally use his fists if I don't constantly remind him to use his best weapon. He was punching robots once.

You don't have to standing at the edge of the wall. You just have to be close enough that the image of the wall stops being blocked. Send Ian away if you have him around and he's crowding you.
Don't stand by the toilet. That's too far to the right.

Is it essential that we get the water chip message on vault 15? I don't remember seeing it, but I guess I missed it while fighting rats. Do we have to kill all the creatures on the vault to see it?