In Section *60.3 Delimiters* of the [TikZ-PGF manual](https://www.ctan.org/pkg/pgf) is written: 

> The <*delimiter*> can be any delimiter that is acceptable to TEX’s `\left` command.

Which are all the delimiters acceptable to TEX’s `\left` command? 
Top Answer
There are 22 TeX *basic* delimiters and some more 'special' delimiters. They are documented in *The TeXBook*:

* [0] The 'blank' delimiter `.`.
* [1-2] Parentheses `(` &ndash; `)`
* [3-4] Brackets `[` or `\lbrack` &ndash; `]` or `\rbrack`
* [5-6] Braces `\{` or `\lbrace` &ndash; `\}` or `\lbrace`
* [7-8] Floors `\lfloor` &ndash; `\rfloor`
* [9-10] Ceils `\lceil` &ndash; `\rceil`
* [11-12] Angles `<` or `\langle` &ndash; `>` or `\rangle`
* [13-14] Slashes `/` &ndash; `\backslash`
* [15] Vertical bars `|` or `\vert`
* [16] Double vertical bars `\|` or `\Vert`
* [17-22] Arrows `\uparrow`, `\Uparrow`, `\downarrow`, `\Downarrow`, `\updownarrow`, `\Updownarrow`
* [23-29] Some special things I have never seen anywhere else but in *The TeXBook*: `\arrowvert`, `\Arrowvert`, `\bracevert`, `\lgroup`, `\rgroup`, `\lmoustache`, `\rmoustache`
List of all the delimiters accepted by \left
JouleV replying to CarLaTeX
CarLaTeX replying to samcarter
@JouleV very good answer!
Far from complete, but a starting point could be to search for "\left" in "The Comprehensive LATEX Symbol List". This will for example bring up "Table 218: Variable-sized Delimiters" and "Table 219: Large, Variable-sized Delimiters". Many more delimiters are defined by various packages