The fastest camera I've ever used was my Minolta Dimage Xt. It was a 3.2MP and I beleive the newer ones are actually faster. Start up time is around a second, and it's ready to take a picture(practically no flash charge time or anything!)
Now, something else to consider is the type of memory used. I had a cheaper SD card in it and it would sometimes take a bit to write. However, when I used some of my more expensive but smaller cards, they would take much less time to write. Compact flash cards are the fastest and usally are cheaper, but most camera's anymore use SD cards due to size...
Hope this helps.
EDIT
Something I forgot, the Minolta is probably not the best one due to it's size. It's a great camera, but the zoom is all within the camera(the lens doesn't come out like most camera's) so it's probably more fragile than others... Plus the lens(at least on the older ones) is in the upper conner so it's probably going to get covered with finger prints
