Backup camera body

Just curious about what kind of camera body you guys have as backups. I am thinking about buying an older model body as a backup in case something goes wrong with my 7D in the field... maybe a 20D or something. It would only be an emergency body, so it certainly wouldn't need to be cutting edge.

For paid work?

The 20D is fine, 30D a bit better and probably not much price difference between them now. Almost pocket change sort of money. Menus + features aside, the controls aren't overly different to the 7D, and unlike the 40D & 50D, they still had the buttons down the left side of the screen rather than below which makes going between them and the 7D a bit easier (not that you use those buttons a great deal unless you need to preview stuff etc, but still...)

Primary - 7D
Backup - 40D

I am very happy with that combination.

Primary - 7D
Secondary - 60D
Back up - (getting soon) T2i

I would love to have a full frame as primary, but that would mean I have to have another full frame as back up. Coz the way I look at it, keep it in the same FOV so the work is streamlined. I don't have to think about difference in framing. And all three shares the same sensor.