1. Probably missed by a few people, south of goodsprings is a little camp site, you come here if you completely do all the tutorial quests, and a guy will beg you to go up the mountain to save his daughter. So off you go only to find a little hidden cache and dead bodies and geckos. Turning around when the geckos are dead the guy will come up and say svcker and attack kill him forthwith and go up a little hill (watch out for the traps) and goodies are there. And a dead guy near a chair and table - it will trigger spooky music/meme if your close enough and you notice the guy's name is Johnny, and from the items close by you determine that it's Johnny from the song on the radio
2. My favourite one, in Camp Searchlight is a church and a basemant (actually 2 churches but the one in the east is the one you want), with the trait you can go in the basemant and get the Holy Hand Grenades only 3 of them, they are like mini-nukes when they explode. Handy for later area's with many mobs coming at you mass style. Without them you get plain old explosives.
3. The infamous aliens, up in the north, quickest way to describe is to head north from the North Vegas gate and when you reach the mountains head west, you will meet them
Some not so useful....
In the Ultra-Luxe Casino when you goto see the detective in the room, go for the bathroom near the body and the taps will turn themselves on... just a spooky thing.
On the Dam fighting for the legion, 2nd tower up the top if your quick enough you will see a UFO dart across the sky. There is another event just further on around the 3rd tower but I didn't notice what it was
A few others that I will leave to other players to list. Some places I seen the meme and heard the spooky music to find nothing, or wasn't quick enough to see it.
