Shepherd's pie is made with lamb; cottage pie is made with ground beef. I'm not a lamb fan, so usually make cottage pie. Here's a great recipe that uses mashed cauliflower instead of mashed potato to top it. I try to eat low carb so it works for me:
http://meljoulwan.com/2010/12/28/paleo-comfort-food-cottage-flower-pie/
I like Mel Joulwan's cookbooks because she'll have 15 different flavor combos to use with ground beef to make burgers, meatballs, etc. Her site has some of the recipes so worth searching for burgers if you're not into buying a new cookbook.
Did someone already say frittatas? Either skillet version or mini muffin version.
E.g.,
https://nomnompaleo.com/post/3717320625/cheesy-n-beefy-mini-frittata-muffins (another good site to search for ground beef recipes).