I can't believe nobody mentioned the taboo against using knives as gifts. I know that is just superstition, but you'd think that BladeForums members would be all up on the lore of the knife. It's amazing how common the taboo is. From the Americas, to Europe, to Asia. Even in Japan, where, ironically, swords are given as gifts to diplomats. It's so wide spread that nobody knows where it came from. I've heard heard things like 'severing relationships', to the risk of cutting oneself, to links to Samurai or Medieval soldiers. Stupid but would be good to know the true origins.
Anyway. I almost always do the penny thing. The giving the person the penny, to buy the knife, you're giving them is about as logical as the original superstition. But, attaching the penny adds a bit of gravitas to the small gift like an SAK and shows that you've put thought into the gift.