Examples I just thought up:
* Variable-scoping-level highlighting—variables in the same scope highlighted the same color.
* "String only"—highlight only strings and literals. Check for language bugs.
* grep-only highlighting—define a set of things to grep for quickly and highlight them.
* block-focused—highlight code blocks so you get an idea of the overall structure of your program.
* No-highlighting: if you really want a moment of clarity on your code. There is absolutely no reason to give up the information highlighting provides 100% of the time, but I could see it being useful sometimes when you need to focus.
And countless more. If I could switch with a quick keyboard shortcut to a highlighting scheme appropriate for any given programming task, it would be phenomenal. I could see it being useful for all kinds of things, and helping to show more information from the compiler than syntax highlighting does already, in a better way. It would be instant visual information, and there's no reason to limit it to syntax like we do currently.
Hmm. Sublime Text Plugin perhaps?