Those artifacts from Roswell that Corso was ordered to distribute for reverse engineering were not 'gifts', at least in the normal usage of that word. But were they accidental 'gifts'? I believe so. Therefore the word 'gift' would suffice wrt what we can say those artifacts turned out to be.
I personally do not believe that ETs are going to give us any intentional 'gifts', at least from their technology dept., until we give up the nukes.