What is an unpopular poker play?

Answer 1

By unpopular I assume you mean disliked, since every action and strategy in Poker is used so much that it would be hard to call any of them unpopular.

What is disliked varies greatly based on your skill level. A well experienced player won't tend to have any disliked plays, but beginner's may encounter several situations that give them difficulties.

One common case is the ultra-aggressive player stalking the micro-limits tables. These guys play almost every hand and raise with reckless abandon. They become bullies since the other players are forced to either fold or join in a very expensive pot.

Short-stacking is also disliked by many players. Not so much because it is hard to beat, but rather because it has a singular purpose of going all-in on ultra premium hands.