To make sure I understand here.
You want a trick that no one has any chance of knowing about, requires no set up, and doesn't use any form of gimmick.
It really depends on what you're considering "unknown". Let me put it in a different perspective - Most card tricks fall into very few categories if you really break it down. Location, transformation, teleportation, production. Either you find a card that was previously lost, a card turns into a different card, a card goes from one place to another, or a card is produced from nowhere.
All the names we apply to those tricks are irrelevant to someone who isn't a magician. Search & Destroy is basically the same trick, to a laymen, as Sandwiches for Mere Mortals. Any trick where you lose a card and find it again - same. Names and methods do not matter to laymen. What they see is all that matters and it is human nature to categorize with what they already know. It's how we make sense of the world around us.
To make it more personal example (at least for me) - metal bending. My spectators see basically the same thing when I bend a coin, bottle cap, fork, spoon, knife, paperclip, whatever. It's all the same, even though they all use drastically different methods.
So I have to ask - why the need for obscurity? Are you trying to make sure they don't associate you with anyone else? 'Cause if that's the case, then it's not the tricks you do, it's the way you do them.