I personally never show my hand if I'm not called under any circumstances. I have mucked four of a kind before. I never talk about the hand either. I tend to think that after I've done this a few times, doubt starts to creep in to my opponents and I end up getting some calls that I wouldn't get, if I showed that I had a winner or at least talked about the hand.

Not showing or talking does make it easier for me to bluff because I don't have to act any differently. I feel like there is some social pressure to show a hand and showing a good hand proves that you are willing to participate in a "friendly game." Showing a bluff is more anti-social and usually intended to needle your opponent. I feel like not showing and not talking about the hand can almost approach the same level of anti-social as showing a bluff. Players think if you aren't showing at all, you must be bluffing.

Showing the nuts if you are a LAG will yield more folds in the future.
Conversely
Showing a bluff if you are a NIT will yield more calls in the future.

both have a +EV

As a fairly tight player myself I do the opposite. I will only occasionally show strong hands to feed my image as a tight player, which allows me to get away with more well-timed bluffs in the future. That's more +ev for a nit than hoping someone decides to look you up because you showed a bluff once or twice.

FYI, I believe the best strat is to never show.

I love the option to show/no show. I think it's a fun portion of the game that you can use both to send whatever 'image' message you want to send and/or change the dynamic of the table one way or the other.

The same show can tilt the opponent in the hand, but also provide 'information' to a thinking player at the table that you want to plant a seed with.

I can see both sides of the argument about showing another reg your cards, but if your game is diverse you really need to keep up both sides of that image and on certain nights it may require a timely show IMO.

I certainly agree that too many loose/weak shows/showdowns can create an extra call or two in your future, but it's up to you to make the adjustments during your session.

I have also mucked quads/nut flushes as well when I wanted an opponent to have some doubt ... Usually someone else at the table will help you with "Gotta show quads." and you can follow up with "Can't show what you don't have." GL

It's a table/player dependent choice there. If I'm at a table full of tight players, I may show some trash cards that I'm limping with. It can loosen the game and get more calls through the flop. As one post above said, when you know what you're doing, it's a +EV play.

You may want to show when you're about to shift gears.
If you have been playin loose but plan on playing tighter show a bluff.
If you've ben plying tight but plan on on loosening up show a value hand.

You have an image. People will use any information to attach an image to you. So feed them a bit of false information and it'll take longer for them to adjust.

Doesn't work against everyone, but it does work against formulaic players who just assign you ranges based on your image.

+1

All of this discussion so far is based on opponents operating on either level 1 or level 3 thinking.

IE Level 1: they will assume, if you show a value hand, that you have more value in your ranges, vice versa for a bluff.

However, an intelligent opponent should be asking the question "What is he hoping to make me think by showing? Because he just showed a value hand, perhaps he is now more likely to bluff." This is level 2 thinking.

Level 3 thinking assumes your opponent knows you will be capable of a level 2 response, and that therefore he should follow showing value with betting value, and follow showing bluffs by bluffing.

So clearly there is an ambiguity as to what you will achieve, which may even backfire by initiating a response other than the one you want. I therefore believe the following things to be true:

-In most instances showing cards is disadvantageous, since it (1) gives opponents more information than they would otherwise have about your play, and (2) if you do not know exactly how they are going to react to that information, you will make them less rather than more predictable to you.

-Showing value hands is almost always bad, since in addition to the points above, it rewards your opponent for making what is necessarily a good decision (their correct fold).

-Since it suffers from all of the above, the only use of showing cards that is reasonably predictable is to tilt an opponent by showing a bluff. Sometimes if I am playing a particularly aggressive opponent (I play largely HUNL), and they have been rude or seem to be beginning to tilt by becoming more aggressive (as opposed to that rare breed who tilt by tightening up, to whom this does not apply), I will show a particularly brazen bluff, especially if they have tanked before folding. When people get tilted they largely call down lighter and play more aggressively, so following the show I will tighten up and weight my ranges more towards value. Showing them that they made a wrong decision has the added benefit of just being straight-up frustrating, and likely to make them more emotional than rational. But I think that any other use of showing results in too much of a guessing-game to be useful.

I never show but i have seen others show bluffs and it gets people tilted.

I think the main factor in whether you show or not show should be based on how well you think you understand your opponents. Meaning you will be more likely to show if you think a) they are not very good and b) you will be able to guess how your past shows will be interpreted by them.

As the poster TheUntiltable pointed out in his (IMO very good) post above, there's so much ambiguity involved whenever you purposefully give information to an opponent (whether it's showing a card or trying to do some sort of complex reverse tell). In an arena where deception is assumed (as is true in poker or any competitive landscape) and players will naturally be wondering "why did they give me that information?", it's just very hard to predict how your behavior will be interpreted. Even for very inexperienced players, that can be a hard thing to guess.

Hence why most experienced players will say that showing cards or doing reverse tells is not a good idea in general. (Though that's not to say that it's always bad; there are good spots for giving away info, and people here have mentioned a few good factors.)

Also I think one of the indirect benefits of showing cards can be to make the game seem less serious and more fun and more lighthearted. If you're playing against players you think are weaker than you, and you think showing cards will induce others to start showing cards or otherwise make the game have more action, there's a lot of potential indirect upside there.