Can something be made which has a private key inside (i.e., the cast secures the key inside, makes it tamper-evident)?
Perhaps a thin metal plate stamped with the private key?
I could see someone wanting a beer stein with a BTC in its base. Where you would never break the stein to get at the value inside, ... or maybe some day you might just be tempted? (I'm assuming the brass casting can be broken to get at the stamped metal plate or whatever is inside, or does the brass fuse together with the steel?)
Or maybe a physical bitcoin letter opener?
Or a physical bitcoin drink coaster maybe?
Or maybe something that encases a Casascius physical bitcoin? Like:
Or lets one be permanently attached? Like:
Lost of neat gift ideas here.