Spaghetti westerns. I don't care which one, just do one.

It's altering the shutter speed, not the FPS, but it has a similar effect. When shooting film, a frame of film is by default exposed for half the time it's in the gate, the other half being used to advance each frame forward. So a frame of film shot at 24fps (i.e. 1/24th of a second per frame) has a shutter speed of 1/48th of a second. This is also known as a 180-degree shutter, since the shutter is a spinning disc and the shutter angle is how much of the disc is open to allow light through.

Because digital doesn't have physical media to physically move, it doesn't need to close the shutter for any longer than the equivalent of a couple degrees, so you can have effectively a 360-degree shutter, or 1/24th second exposure per 1/24th sec frame. Longer exposure means more motion blur per frame, which makes it feel something like having a higher framerate capturing the motion.

PUBLIC ENEMIES was shot at 24fps just like COLLATERAL was. But the style feels appropriate for COLLATERAL and not for PUBLIC ENEMIES (and also the effect is less pronounced in darker imagery).