You need to watch more of those court shows on TV. This issue comes up in just about every case.
If it was a gift, then person B can do whatever he/she wants to do. Person A has no legal rights. Of course, person A will try to lie in court and say it wasn't a gift. However, person A must prove that in court. And person A has an uphill battle. If person A didn't give it to person B, why does person B have it in his/her possession? Plus, person B will testify in court that it was a gift.
The result is person A vs. person B's word but person B has one piece of physical evidence in his/her favor (the fact that he/she actually has the item). Thus person A needs to have strong evidence that it wasn't a gift. Strong evidence could include a written contract or payments from person B to person A for the loan of the item. A receipt is not strong evidence because person B confirms that person A bought it. Who bought it is not what is being disputed. This is especially true because the receipt date is often a week before person B's birthday/Christmas, even more reason to think it was a gift.
But in reality, why all the fuss. A used 27" TV is worth very little. Don't sweat it. Let person A sue, you'll probably win. And if you lose, you lose something that is virtually worthless.
Edit: I just saw that it was your father. Why are you (and your father) distroying your relationship over a worthless item? What is more valuable to you, your relationship with him or a stupid TV?