Milt Kort's All-Outs Think-Of-A-Card by Ron Bauer

In addition to being a delightfully direct discovery of a thought of card, this is the ideal way to learn to understand and master the basic principles of "outs" without the usual hazards.

Milt Kort invariably used this stunt to secretly reveal the sophistication (if any) of strangers before trying riskier stuff. Use any deck; any time.