One of my friends is starting at the Yehudi Menuhin (or however the hell you spell it) School this September. (It's a really exclusive music school). She plays classical guitar, and has to keep the fingernails on her left hand long. As a leaving present, I made her these:
fingernail protectors! Along with some personalised manuscript paper (as she has all her best composition ideas in the middle of the night, it says "Laura's 3AM Music" along the top) and a CD of flute and guitar music (because I play the flute and we used to duet a lot).
Small ball DK weight yarn
3 double pointed needles ... not sure about size, but tension needs to be tightish
CO 8 sts to one of the needles
*K1, Sl1 p-wise * rep from * until end of row onto another needle
Carry on knitting in this way on two needles until work is long enough to cover fingernail
Sl first stitch onto other needle, then Sl the second onto different needle. Sl alternate stitches until there are four on each needle. The work should resemble a little open bag.
Cast off. Turn inside out. Tidy ends.
For thumb: CO 12 sts and do same as for little finger
For other fingers: CO 10 sts and do same as for little finger.
I'm not sure if these have any kind of practical application, as they fall off as soon as you move your fingers quickly. However, I think they'll be appreciated as a joke present ^_^