Well, a new SLR feature could be to switch on a color balance/adjustment system, similar to white balance but with the addition of RGB controls for each channel. I imagine the interface having slider bars per color channel accessed through the menu system, and the results would be similar to the "Hipstamatic" application, but with full manual control of course, and not tying down the photographer to any presets.
I imagine this would be a feature mainly for fun, and thus would be introduced in a xxxD or xxD body. Also a side note to my idea, this would not be destroying the IQ like a holga lens/camera, simply provide a way to control color manipulation that is not done in post processing....
For those not familiar with "Hipstamatic" or any similar apps, it takes digital photos on a smartphone and renders something that looks like it's been processed on old damaged film. Results would be similar to these but with much better resolution due to the capabilites of the lens used and DSLR body attached. The following photos are not my own, simply linked off the photojojo forums.


