Best "bang for your buck" supplemental exercise(s)?

(Besides hangboarding.)

I want to add a couple exercises that don't take up too much time or energy so I can focus on climbing.

Today I was thinking about how the front lever is a pretty efficient exercise since it works your pulling muscles (lats esp) and core at the same time.

Pull-ups are also very relevant to climbing, and you can engage your core with those as well.

Both of these can be regulated in intensity and can be done bodyweight as well which makes them convenient.

Any other contenders I should consider?