Some dreams I have had are the feeling of falling (that feeling in your gut) and waking up just before I hit the ground, dreaming I'm in some freaky house with a group of friends and we are being haunted by some weird creature and I always look to hide in some small place where it's small and I can see everything around me.
Funny dreams are when you have things happen to you in real life and they become part of your dream (e.g. In my dream my hand started killing me and I woke up with my puppy trying to pull on my arm). The dreams I hate are when you are fortunate (for example I dreamt I had all these pokemon cards everywhere (I was only 10 and pokemon was cool then), anyway I was looking for this particular card and just before I find it, I woke up.
Sometimes if I can't do a maths problem, I dream about it.