[Talking Poker]

....it depends.

I've played in games/tourneys where showing (let alone announcing) your hand is allowed and also in games/tourneys where it's not.

On "the boat" here (this seems to be the most common rule, in my experience), if you expose your hand and there is any action left behind you (including someone needing to throw in just a few more chips becuase they bet 50,000 and you pushed in for 50,400, thinking you were calling because you had the smaller stack), your hand is dead. No questions asked. If there is no action left behind you, then you can turn both your cards up and try to get a read on your opponents reaction if you like. It doesn't happen often, but it is allowed.

In the big NL cash game I play here, this happens regularly.... people showing or asking to see one card when they have a big decision to make. In heads up play, this is perfectly fine with everyone.