I think 'print' is underrated as a debugging tool, particularly when you don't know what to look for. You can at least start zeroing in on the line where things fall down, go boom.

That said, I use gdb a lot lately, since my new job at work is getting some existing C code up to snuff for a new FDA-mandated standard.

Still, I love the debugger in XCode on OS X. It's like most things you get from Apple. You think it's nice, but when you use other similar tools, you really appreciate just how good it is.