Fingerprints, hands down. Love it, love it, love it. Just really fascinates me. I think it has something to do with the fact that no one, not even identical twins who shares the same DNA, has the same fingerprint. It's cool beyond words.
I bought Cold Burn in February and I still haven't started reading it! Blame it on Hannibal and the other tons of books I got for my b-day. Those of you who have read it, is it any good?