Vim and Emacs (yes, I'm schizophrenic).
Once you've gone the Way Of The Emacs, there is no reason to use vim... unless you have some internal application written in vimscript, of course.
Viper just gets you insert-mode and command-mode. It's still Emacs.
But hey, these two programs are great. I've tried other IDEs, but always end up coming back to one of those two for real work. Some things are easy in one and annoying in the other so they complement well.