Extraction elements

Extraction elements are, as the name would suggest, elements relating to the extraction process. Specifically, they include any methods that can and have been used to extract an answer, clue phrase, or instruction in a hunt puzzle. While there are certainly many ways of doing so, extraction elements only become so after having seen sufficient (as in two or more times) use.

Core Characteristics
It's much easier to determine what can be an extraction element than what is exclusively an extraction element. This is because there is ample opportunity for what would normally be considered an extraction element to be used in a non-extraction format. However, focusing on what is primarily used as an extraction mechanism allows for a bit more picking-and-choosing for inclusion.

An extraction element must be capable of extracting a word or phrase, either as a whole or letter-by-letter (or in rarer cases, segment-by-segment). However, with the wide range of things existing that are capable of mapping to the alphabet or particular words/phrases, some elements have to incorporate the more specific methods, such as any number-letter substitution being filed under Alphanumeric Substitution Cipher.

It's also important that an extraction element does not need to be used to extract the final answer in a puzzle in order to be considered for inclusion. Since extraction as a concept extends to things like intermediate/final clue phrases and intermediate puzzle instructions, the criteria for extraction elements must extend to them as well.

Subtypes
Extraction elements can primarily be broken up into groups based on the method by which they extract.

Decryption
Decryption extraction involves deciphering a code or cipher, or at least something that can easily map to letter or words in a given language. That means that not only are 'traditional' codes used to obfuscate information (like the Caesar cipher) members of this category, but systems for regular, open communication are as well (such as flag semaphore).

Visual Extraction
Visual extraction involves systems that result in some kind of image or visual representation of one's final piece of information. This includes both actions taken to generate an image (such as playing Charades) and ways of expressing an image (such as bitmaps).

Letter and String Extraction
Letter and string extraction involves taking specific portions of words and phrases based on various criteria. That criteria can be the position of them within the strings, an outside value or marking that indicates what to take, or a relationship to another string.

Other Extractions
As not all extractions fit neatly into the other three categories, the miscellaneous ones will be lumped into this category. These include things at both extremes of the puzzle-involvement spectrum, from heavier-than-normal (odd-one-out), to the minimal (extraction by reward).