theory11 — Magic Tricks & the World's Finest Playing Cards
I can't beleive that i the first to say it but "Clipshift". Any of the color changes could be applied as a vanish. I would also reccomend the " Half- Vanish" by D+M . The rub-a-dub vanish answer above would be pretty effective as well.
Sorry to open up an old thread, but for a reference to this type of request, the rub-a-dub can indeed be used, or at least a variant. If the card is signed on both sides, you could use the same method lot's of people have tried to rub-a-dub vanish a face up card- have a card in full palm in the 'receiving' hand as you push off the card to be vanished on top of the deck. the palmed card is deposited on top as it apparently takes the signed card. A simple side steal would bring the card back into full palm after the vanish. The same principle can be applied to the tent vanish.
Personally, I would use gary Kurtz's longitudinal steal, which is sort of like a vanish you would use for a jumbo coin.
CL