Can a gift be legally revoked?

Your friend can legally "ask" for anything, but an unconditional gift cannot be revoked except under circumstances which don't appear to be n play here (gifts in contemplation of marriage, gifts in contemplation of the death of the donor).  However, your friend may claim that he didn't make an unconditional gift, but rather that he, for example, was only letting you use the stuff until he got a new  place, or was letting you use it only as long as you let him use it in your home, or something else.  If the judge/jury believes you that it was an unconditional gift, you should win any lawsuit, but there is no guarantee that the judge/jury will not believe your friend's version.