A new user will often not remember whether a symbol he has in mind is a function or variable, so he doesn't know whether to use C-h f or C-h v to get help for it. For example do I use mark or (mark)? C-h v mark TAB TAB, it's not there, C-g C-h f mark TAB TAB, there it is. Later I'm looking for mark-active and try C-h f first, and again have to cancel and switch. Also, when a symbol is used as both a function and a variable, a new user would want to know about this, but he's not going to find out by using C-h f or C-h v unless he manually tries both every time he looks up something new, which is inconvenient.
A help command which provides completion on both functions and variables, and if a symbol is used as both, shows the help pages for both, solves both problems. The attached patch is a simple union of describe-function and describe-variable to do this. It triggers bug# 13105, but I sent a fix for that.

BTW am I supposed to send little things like this to emacs-devel, or to bug-gnu-emacs, or just post on the wiki? It isn't a bug, but some of the docs say the bug list is also for new features and patches so they can be tracked by bug number, but they also say if a patch needs discussion then it should go to the devel list. Maybe it's superfluous, not worth cluttering Emacs with it.