Farmer's walk is probably the best single core exercise.

The McGill "Big 3" are bird dog, side bridge, and curl-up.

This article discusses the 6 core movement patterns (3 concentric and 3 "anti"): https://www.t-nation.com/training/adamantium-abs-6-core-exercises-you-need?utm_source=tnation&utm_medium=email&utm_campaign=weekly_dose-20-07-19