I remember seeing a lot of dream/nightmare threads around. Funny, but they seem to have all gone when I want to reference them. I did find one existing thread on this topic, about cool dreams:

Coolest dreams you EVER had!

There was another one about nightmares which superdecimal started a while back, but I think that is too old to revive now...not sure though.

EDIT: Just found another one:

What has been your worst Nightmare?