I'll go with a pregreen nose, or poof that is not as big as the entire front opening of the green, is about 2-3ft high and maybe 3-5 yards in diameter, like a pimple or however you'd like to call it. The idea is it provides a bit of mystery to a shot landing in the pre-green apron, that can give any of severa potential deflections right to a pin, or off to a side or stop the shot up short of the green. I love the one at 14 Wild Horse.
Also, I'll offer up consideration of a surprise small pot bunker behind a green. One that only gathers minimally, not widely.
Generally, I'd say false fronts are always on good holes... maybe someone has specific of a horrible one.