Ive tried using gdb with Emacs (via GUD[1]) if that counts, but it never worked out for me in the sense that I felt I got anything extra in return for the investment.

Maybe there's some special things I forgot to do, but out of the box GUD definitely felt (too) minimal for me.

Lately I've used LLDB when working on the .NET framework, and that seems like quite a reasonable thing to work with too at this point. I'd love some emacs-magic for this too :)

[1] http://www.emacswiki.org/emacs/GrandUnifiedDebugger

I generally use cgdb (or gdb -tui) but for some complex tasks, I use the ddd gui frontend. It's not a pretty gui and the usability is not great but the visualization it provides is excellent. I've used it for complex data structures and debugging numerical algorithms. Getting it to display structured data as you step through the code can be super helpful.

That being said, I hope that lldb will catch on and there will be some decent front ends for it. The GDB-MI (machine interface) used in debugger frontends is quite limited and clumsy. The lldb debugger should be a lot easier to embed in a project as a library (as opposed to using pipes and gdb-mi).

Qt Creator's gdb integration handles the basics well (I haven't used it with lldb, but lldb supports the gdb MI protocol so it should at very least "work").

https://cgdb.github.io/?

Qt Creator is great for Qt. KDevelop and Emacs gud-gdb also provide nice vanilla frontends.