An awesome feature would be ability to declare comments for function arguments. The comment would appear in an additional bottom line with tooltip help - for the current argument, of course.
This would be nice, because even with long argument names, we sometimes still cannot describe them properly using name alone. It's a pain to constantly switch to header files to get additional help on arguments. Having the argument variable type / name is of great help, but not always enough.
Example, how comments could be given:
function( / function desc */
int arg1, / arg1 desc /
int arg2) / arg2 desc /
Even better, if it could parse any style comments, as long as they are given in the same line:
function( // function desc
int arg1, // arg1 desc
int arg2) // arg2 desc
This second style looks nicer.