I wanna say standing ohp as it’s my favorite exercise and I currently can’t do them in my space. However, I’m going with squatting too. It’s the one exercise that I feel affects every other movement I do. What I mean is, if I had stick legs I wouldn’t have leg drive for push days. Also, squatting is something I can throw into any day and feel good about it. I also used to hate squatting and early in my gym days I admittedly never worked legs haha. Times have changed.