Hit him with storage fees!
The definitions, laws, and basically what constitutes a valid gift and the opposite of it which would be wrongful taking as well as charitable contributions and remedies, including the action of Replevin, come under the personal property laws which are in turn part of the overall Property Law; that would be personal and real and they are not state specific.
I really think the fact that he was a tenant of yours may well be a handicap for your attempt to explain the furniture as gift but may also turn out to be a blessing in disguise, depending on what course of action you would want to pursue and just how strongly attached you are to the furniture.
One course of action would obviously be to answer his complaint for replevin and appear at the appropriate hearing and argue your case for gift which due to the landlord-tenant relationship might be a bit of a hard sell. If you are in a real fighting mood and want to mix it up with this guy just for the heck of it, then another course would be to argue at the hearing that the action for replevin is not the right one in this case and that the plaintiff should file a regular civil suit so that parties may be afforded the tools of discovery, request interrogatories, and conduct depositions and what not.
Now, while litigation and courtroom sparing may be quite fun (it is for me) and gratifying in some ways, it could nonetheless be time consuming and a bit expensive both financially and psychologically, so you may want to consider turning the tables on this person come the hearing and come out smelling like roses and laugh all the way to the bank.
Since he was a tenant of yours and claims that he had merely left the furniture there for safekeeping, then why not just counterclaim with a demand for payment of storage fees covering the time period in question; which payment you are FULLY entitled to as a landlord or even as a bailee.
fredrikklaw