parallels or bootcamp or both?

Hi, newbie here. Wanting to retain ability to play a few favourite PC games on my new imac, can I run Bootcamp together with parallels on the imac? I've heard it may struggle on parallels with a resource-hungry game, in which case I can boot into windows from bootcamp, but for some work and graphics apps it would be cool to have both windows and os x available on the same desktop. Do I have to choose either Bootcamp or Parallels as an install?

You want to run bootcamp for the games - but you want to run parallels or vmware on top of it. Run bootcamp when you are running a resource hog - run the Virtual Machine from inside your Mac if you need to get to anything - do updates, etc. Best of both worlds.
See this document
Parallels Desktop User's Guide

Thats great - thanks, I was told they were mutually exclusive and you could only have one or the other on your drive.

You can have both, I used to have parallels 5 and bootcamp at the same time.

In fact, they use the same Windows install, so whoever told you they were mutually exclusive either has very old info or was talking out of their ... um ... hat. Yes, hat.