What is your 'why have I never done this before!?' workout?

Today I did this upper body strength workout with Daniel:

https://www.fitnessblender.com/videos/upper-body-strength-workout-guaranteed-muscle-burnout

I've never done it before and I swear my arms were shaking so much, it's no lie when it says 'guaranteed-muscle-burnout'!

I thought to myself, 'why have I never done this one before!?'

It has served me inspiration for this week to try workouts I've never done before. I'm hoping I might find another gem like the one I did today.

Can you remember a workout you did where you couldn't believe you hadn't done it before? :)