A paper wallet filled with those 100$ in Bitcoin probably is the best.
Mining equip? If she/he's an enthusiast she/he might enjoy some mining for fun, allthough it isn't worth it, even when the equip is gifted and thus there's no initial investment.
A share in some bitcoin project?
If he/she's of the charitable sort making a donation in her/his name might be nice, maybe some of the charity projects give out nice plaques like the WWF is doing.
That's my ideas.
a friend of mine has something like that. made of wood.
This is a VERY nice idea. I'd probably go with that.