I have arachnophobia, and this dream scared the hell out of me.
It was dark out, and I didn't want to walk home, so I went to my friend's house. They gave me the guest room to sleep in...and so I got in bed. I pulled the covers up, and just as I was falling asleep there was this tickly thing on my legs. I get up, flip the blanket/quilt over, and I see this GIANT YELLOW AND BLACK THING WITH EIGHT LEGS STARING AT ME. I was freaking out. I got an adult, the adult did something with the spider, and then it was gone. So I went back to sleep. Sometime after that I woke up and found the spider again. I whacked it with books. And yet, again and again, it always came back. Eventually I went downstairs and found that someone left the computer on. This game was on the screen, and I found that even level one was crazy hard. It's like Touhou on Lunatic at 100% speed. Except it's worse, like a Master Spark (see "giant laser") that's completely unavoidable. With a phoenix. I went back upstairs and guess what was up there? The spider. The dream ended when I decided to run home cause I was the only one who got a spider in their bed.
And I woke up and my first thought was check for spider.