What is a good substitute for heavy whipping cream?

Half and half is what I use if I don't have heavy whipping cream

If you don't have any more cream, you could use a little whole milk to make up the last 1/2 cup.

What are you using it for?

Just regular heavy cream. Depends on how you're using it but sometimes you can substitute creme fraiche, mascarpone or whole milk Greek yogurt.