CodeQuery is a tool for indexing and then querying or searching C, C++, Java, Python, Ruby, and Go source code. It builds upon the databases of cscope and ctags, which are processed by the cqmakedb tool to generate a CodeQuery database file. This can be viewed and queried with a GUI tool. The features include auto-completion of search terms and visualization of function call graphs and class inheritance. The following queries can be made: Symbol, Function or macro, Class or struct, Functions calling this function, Functions called by this function, Class which owns this member or method, Members and methods of this class, Parent of this class (inheritance), Children of this class (inheritance), Files including this file, and Full path for file.
vxref provides integration of the xref tool into vim. The xref tool is a cross referencing and refactoring tool with a free version available that parses C and Java code, and a paid version that parses C++. vxref brings solid auto-completion (as opposed to all sorts of flakey varieties such as omni-complete) and accurate code browsing with scope information to vim.