Wide grip L: 1 rep for 5 sets.
One arm assisted: 1 rep for 5 sets, current strength level has my assisting hand at shoulder level at the bottom of the movement. I also add an L at the top of the movement to make it even more tough.
Front lever row, straddle: 1 rep for 5 sets, not a pull-up exercise per se but still an upper body pulling movement.
More exciting when all 3 are combined into a super set.
These exercises, their variations, as how to execute them can be found in Coach Sommer's Science of Gymnastics Strength Training available for free on the internet. His focus is primarily on doing fewer reps of a harder variation of any exercise. According to him, once you can easily do 5 reps on any exercise, it's way too easy for you and will not give you any additional strength gains, and so move on to the next harder variation of that exercise. You can do this by either decreasing the leverage (such as adding an L to a standard pull-up), or increasing the resistance (such as wearing a weighted vest or holding for a few seconds at the top of the movement before coming back to a dead hang). Also there is a strong emphasis on core strength as the variations get harder so you end up training your core as well.
Basically, if we're talking max strength gains, it's not about the number of reps you can do, but the amount of tension you can generate in your muscles. You can do 15 to 20 standard chin-ups to impress your friends at the park, and it's also generally good for strength endurance, but during training focus on practicing harder variations where you can barely pull off 3 reps. At a point, standard pull-ups or chins just become extremely boring or just great for a warm up.