Probably a full/punch wedge, if I remember correctly goes around 50% of the full distance. What you mean ethical? Like divots on the green? There's no rule saying you have to use a putt on the green. If you were in a multiplayer alternate shot and their partner got pissed then they have a point, it can be conceived as "not trying" as even the worst putter on the planet should have a higher make percentage with a putter than a wedge, a driver or whatever the guy in your game was doing.
Effective I mean... technically I think there's some very specific positions from which a wedge could leave you closer than rolling through the break if you have practiced it. That said virtually every single case I've seen of players using this, and I've seen quite a few, is something completely different: a scuffed attempt at "flexing" by hitting a driver from 3 feet instead of a putter like a normal person. Then when they miss, they get flamed and they're the ones to quit the game. They're weirdos but as long as they aren't bothering anyone else just let them be cool dawgs or whatever