I wrote a module that is a completely customizable menu because we had a need to do something like that for our company intranet. It allows rendering as a treeview or a menu (and the menu can be horizontal or vertical); items can have icons+text, or just icons, and items can point to a user record, a tab, an external resource, or a file from the file manager.
It is currently not available for public use, and I can't exactly take my code that I wrote as part of my job and resell it (that would be dishonest)... but I do have plans on creating a "commercial" version of it from my "spare" time at home and getting it out there. Unfortunately those plans fall behind other projects I'm working on in my "spare" time and likely wouldn't happen until possibly late Q3 or even Q4 this year. (doesn't help that the end of Q3 also coincides with when my second daughter will be born).
I wrote the module because I couldn't find anything out there to do this same thing... but that doesn't mean they aren't out there. I just couldn't find one. I bet it wouldn't take long before somebody else builds one and beats me to the punch, but I just don't have the time to get my own version out there. I understand John Mitchell has something similar with his CSS only menu, but it appears to be template driven (not sure how that works... probably XML templates in the file system?). I didn't learn about that until just recently anyway, so I had already created my module.
If you want a demo of how my module works, maybe I can help set you up something on my personal website so you can take a look at it... if it is something that would work, perhaps I can push up the schedule and get it out there sooner.
If you find anything else out there, I'm interested in hearing about it though.