I would love to be able to control the start position of playback of a sample. Obviously, sustained samples would be best, but it would open up all sorts of wavetable-esque possibilities...
Actually, ideally, there should be two 'Start' positions: one for the actual start of the sample replay when you initially press a key (and this one is the one which needs to be controllable), and another for the sample that plays immediately after the last sample in a loop when you are holding the key down (and this one needs to be fixed for the sample!)...