Scientific research has confirmed our suspicions: 97.839% of manuscripts written in Courier are epically, wildly, apocalyptically terrible. Better switch to Times or Helvetica, y'all. Sorry. We know they're boring.
CLARIFICATION: What we meant was that 97.839% of writers who use Courier are epically, wildly, apocalyptically terrible. Sorry if that was vague. As far as what you should use for your ms, Times is industry standard, but the only font that will cause us to reject your book without even looking at it is Papyrus.