theory11 — Magic Tricks & the World's Finest Playing Cards

gaffs

I do not use a lot of gaffs but I have a preference for the double backs
 
It's like asking what the best sleight is. It's all relative to what you want to do. Even asking what the most versatile gaffed card is is problematic because that depends on the same thing.
 
I think the best gaff cards should be undetectable. I mean there are some cool effects that you can do with cards that have half a face half back on them etc, but these effects shatter to pieces if your spectator asks to see the deck, or even if you aren't careful whilst shuffling and squaring the pack etc. I think a good old double backer is pretty much all you need as they are easier to hide.