Can you capture a still from streaming video with a good digital camera?
I have to take some self-portraits for promoting my singing career, but my Canon Rebel is going to be too slow to see the results. So I'm buying a digital camera. I plan to get HD, and enough megapixels, but I'm wondering if I can cut stills out of streaming video, or do you need a good camcorder for that. If so, how good a one would I need?

It’s not the equipment, but the technique. The Rebel is very capable of capturing great still images.
HD is much lower resolution and while you can grab frames, they won’t be anywhere near as good.
I suggest that instead of buying an expensive HD camcorder, you get a good photographer (even an art student good with photography and lighting) to take your photos. It’s just not a good idea to take your own photo. If you are committed to taking your own photo, try using a digital SLR with live view and hook the camera up to a monitor, so you can pose adequately, then use a remote release for the camera.