Given a handful of transactions from a single individual, are there any techniques to try to infer/deduce what client the individual was using? In other words, do any commonly used clients leave a "fingerprint" that can be used to recognize which client was used, based on the information in the public blockchain?
For instance, maybe some clients have a recognizable pattern of how they make change, or which script code they use for transactions, or have some pattern regarding which of the addresses in the output list are for change, or have some pattern in the transaction amounts or the random numbers used in the transaction? I'm just brainstorming examples -- don't take these too seriously.
So, are there any fingerprints that are left in the blockchain that might reveal which client I'm using? Even probabilistic attacks ("there's an 80% chance you're using client C") are relevant.