Saltines, oats, white bread soaked in milk - they’re all good (I’ve tried all three plus a lot of other good options, including stuffing mix). One of the main tricks to good meatloaf is not to over-mix whatever you add. Just a minimum of stirring, and toss it in the oven.
I have to admit, putting bacon on top of meatloaf is a pretty awesome idea, too. I’ve never had a packet of bacon last past lunchtime in my house, so I don’t know if I’ll ever get a chance to try it....