In terms of a pristine comparison sample taken specifically from an individual for purposes of comparing it to a crime scene sample, the preferred sample is a blood sample. It strikes the appropriate balance between ease of sampling and ability to obtain a sufficient amount of DNA that can then be easily tested. So a blood sample is the best.
When you talk about a crime scene sample, it's a very difficult question to answer. It depends on the amount of sample available, the conditions in which it's been stored, etc. As Ray has pointed out, we receive everything at the laboratory, including the kitchen sink.
So for a sample from an individual, a blood sample is the best sample for our purposes. For crime scene samples, the more body fluid present, the better, but again, it depends on how it's been stored.