Fingerprints. Dental records. DNA. Retinal patterns. Other physiological features which can be or are used as unique identifiers?
I’ve heard in addition to the above: footprints; ear shape; voice print. But nothing really substantive to back them up.
Besides retinal patterns, the patterns of the iris can also be used.
Butt cheeks 
I think it’s a no on ear shape :
Lines on ones lips are pretty good. Fairly simple for computer generated id systems. But the issue is, um, data acquisition. You know, sanitation, creepiness, etc. But once cheap long range digital cameras become commonplace, they’ll be able to do scan you from 20 feet away. Then everyone will start wearing thick lip gloss when going to WalMart.
Note that bite marks are sometimes used in criminal trials, but I wouldn’t convict someone if that was all the evidence.
Footprints are as good as fingerprints, but you have to have good copies made ahead of time. Usually not available for iding a body found in a ditch.
Voice prints are more magic than science. Many European intelligence agencies have proclaimed the Bin Laden tapes to be fakes while the CIA says they’re real. Pretty much in the same class as “lie detectors.”
What about a map of the lines on your palm?
About a year ago I remember watching a show on one of those educational channels (TLC, HIST, COURT TV, DISC, etc.) that covered, IIRC, a bank robbery where a man dressed as a woman, lipstick and all, was trying to escape the bank and ran face-first into the glass door leaving behind lip prints. Subsequently, he was identified by the lip prints left behind and convicted of armed robbery.
I tried to find it online but had no luck. But, then again, I’m quite lazy.
How about scent? Except in those with poor hygeine, it wouldn’t be readily apparent, nor do I think any technology has been developed to detect it, but supposedly a dog can. Years ago, I remember seeing a documentary on tracking dogs which stated that each individual person’s scent is unique, and cannot be masked, even with perfumes.
So, maybe “body odor” counts as a physiological identifier.
X-Rays. Or bones, period. By superimposing a photo of a skull over a photo of a person (at the same angle, etc.) you can determine if the skull belongs to the person in the photo or not.
Lip and ear prints are unique. I believe a recent case did admit a comparison of an ear print to that of the suspects. Palm and footprints, like fingerprints, are also unique, but are usually not kept on record. These types of evidence can only be used when there is a known suspect to compare the prints to, while there are several fingerprint databases that can be checked for an unknown print.
In this case a man was found guilty via an ear print that turned out not to be his. The danger of “cutting edge” evidence.
Another admission of ear print evidence
Lip prints haven’t been subjected to serious study yet, from the looks of things. The Charlottesville Police claim to have used the method at least once. It sounds viable, just not fully documented yet.