Depends on the state, and source of the gun, and your conscience.
Technically, you probably can’t do it as a surprise present. Maybe a card with a note, and you both finish the deal at your local FFL dealer.
Not read sure, but you just don’t put one in a Christmas Stocking.
Let’s say Illinois for instance.
Can't you truthfully declare you're buying it as a gift (on an FFL form)?
In any event unloaded, in a box, in a stocking is a fine American idea if the stocking is out of reach of children.
So, does the legal distinction have more to do with whether it's intended for a criminal enterprise, or whether the person ultimately receiving it is legally permitted to do so?