Branching/Progressive Anagrams

The branching anagram is a method devised, as far as I know, by Stanley Collins in 1920 and has been tinkered with by numerous thinkers over the years. The principle at the core of the method is that a person can think of a word, and as long as there are a limited number of options to choose from, by discovering which letters are present in the word they chose, their word can be determined.

See:

The Prodigal by Atlas Brookings

https://thejerx.squarespace.com/blog/2016/10/5/transgressive-anagrams

P.A.TE.O. Force

P.A.T.E.O. Force (pick any two, eliminate one) is a method of forcing a particular object from a set of objects created by Roy Baker. It was first described in Baker's Bonanza (page 40) by Hugh Miller (1968).

It involves the spectator and magician in a rotating selecting and elimination process, leaving only one object from an unlimited number of objects.

The method may be disguised in a multitude of ways within card tricks, mentalism, stage routines, etc.

Magicpedia: P.A.T.E.O. Force

Stepping Out Onto the PATEO

Mind Sniffing - Ian Rowland

Pins a large folded jumbo card onto a spectators shirt.

Has audience think of a number between 2 and 21. 

Chooses someone in the crowd to reveal their number.

Picks up the cards from the glass. Counts the number of cards, faces toward the audience, till he gets to the number and places that card back into the glass. 

Reveals the Jumbo card matches the card in the glass.

Image Projection, Pepper's Ghost, etc

Two Way Mirrors: Pepper’s Ghost Illusion: Complete Guide

Wikipedia: Pepper's Ghost