I'm going to put my leftover roast beef into a casserole type thing - it's quite lean so will also put some bacon in for the fat and some flour to thicken the sauce, carrots, parsnips, onions, mushrooms, herbs, beer and stock.
With mashed potato and mashed swede.
EDIT: Oh I also have a bit of Yorkshire pud left (I made a big one last night), will reheat that too.