A ray of hope for nightmare newbies is, you can get used to them. Your heart will stop racing eventually, the cold sweats will (mostly), maybe your head doctor will exorcise them for you, but if not, you can get used to them. It's not that you stop being afraid of them, you just stop caring you are afraid.
For all practical reasons, I only have nightmares and never have pleasant dreams. Here are some common themes:
Nuclear holocaust
Getting raped by men or turned into their slaves
Getting stabbed to death
Falling off very high places and hitting the ground (when I had a mattress, this would be bouncing when I woke up too)
Drowning
Getting *severely* humiliated by women (this one's kind of sexy too, but it's still not pleasant)
Sky collapses, this one often has a martyr component too where I save lots of people but die myself.
Completely paralysed and body moves around on it's own
Fighting with people and all my blows do nothing while theirs tear me to bits
Being in survival situations and eating babies to live
People I know who have died being alive and doing very bizarre things, I know something is wrong with them being there but can't put my finger on it, when I realise they're dead I wake up
Being chased by huge armies
Those are just the most common themes, all my dreams are nightmares and have been since being tiny so I usually aren't even bothered by them, I quickly go back to sleep and forget them. Exception to this though is quite frequently as soon as I fall asleep I will drop immediately into a nightmare. Again I forget what they are all about but I can remember the feeling of extreme terror, I know I'm asleep though, sometimes I force myself to wake up, sometimes I just think screw it and stay asleep, don't remember nothing about it after either way.
Oh, and I feel what seems like physical pain in dreams too. I read that's not supposed to happen, but it does.