I would like to disable one of the Responsive layouts. Whatever the second smallest layout is before it switches to the mobile view.
If you aren't compiling LESS, the best way I've found is going into bootstrap.css and commenting out the size you don't want active. The CSS is pretty well-organized, and disabling one of the sizes doesn't appear to affect anything else.
(Of course, you have to be careful you don't re-enable them when updating Bootstrap.)