The sissy squat is a classic quad builder. It's normally performed with bodyweight or while awkwardly trying to hold a plate across the chest. It really targets the rectus femoris, one of the quad muscles that's understimulated by standard barbell squats.
Here's how to ramp up the sissy squat with a landmine device. (No landmine? Just shove a barbell into a corner against a towel.)
Set up with the barbell anchored down low and then have the bar at your chest in a goblet grip.
What's cool about this variation is that if you stand further back, the landmine essentially just acts more like a core-challenging hand support than resistance. But as you move your feet closer and your knees go forward and your torso goes further back, you'll get challenged more by the resistance.
If you're struggling with it, you can play around with letting your hips bend too and making it more of a heel-elevated goblet squat.
Set up with the end of the bar on one shoulder. It can be helpful to have a plate on the bar for your shoulder push against for more support. You'll need to play around with your foot distance, but once you find it you can get a nice arc motion.
The landmine arcing motion works really well here because as you bend your knees and they go down and forward, the bar will follow a similar line. With the last version, it really challenges the core, whereas this one puts more emphasis on the quads.
You can also play around with the amount of hip bend if you're struggling with getting the motion down.