Cscope in vim to jump between caller and callee (examine relationship). See where symbols are used. Jump to global definition. Could not live without cscope!
Yes this is how I use it and I love it. I think some IDEs havee similar capability but for vim users cscope is an great way to understand large code bases by quickly jumping through callchains. There's a 'Using Cscope with Vim' tutorial on the page that covers it.