A lot of wiki-style services (Confluence, Coda, Tiddlywiki + autocomplete plugin, etc.) support quick linking of other entities or pages in the wiki through @-mention or [ ... ] type syntaxes, giving you a dropdown of possible options when you type the initial character. (Even Google Docs has something similar when you open the hyperlink menu - it'll autocomplete likely options as you type a doc name.) This makes cross-linking pages much easier, which can be a major part of writing pages. Adding this functionality would be extremely useful.