showing cards

this was brought up in another thread as a tangent, figured id put it in the limelight for a second.

a) heads up, on the river, 1st to act bets. 2nd to act exposes his cards. is this considered anything automatically? does he have to call or fold or anything? what are the rules for exposing cards like this? (or any similar situation in which the exposed cards were meant to get a reaction from the other person)

b) whats with all the show-one-card during a showdown BS ive been seeing in holdem lately? i play at a number of local tournaments (both free and money) and so often it will come down to heads up and player one will show his ace, player two will show his ace, they will each ask the other "what's your kicker" and be hesitant to show. what is with that nonsense? if i call a bet on the river, ive paid to see the winning hand -- all of it, correct? my thought is that if you only show one card, youre essentially mucking the other. if youre gonna be embarrased by your weak kickers, DONT PLAY THE HAND.

what's worse -- and this i consider near cheating -- is when one hand will show an ace for a single pair, then the other will show his ace with good kicker, then the original person will show his kicker and it is a second pair or trips or something.

c) similar as b... in omaha, i always show all four cards during a showdown, just in case ive missed something, since "the cards call themselves." more than once, someone has shown two cards, seen he was beat, check his other two hole cards, and expose one or more of them to make a better hand. whats with that?

[i have no problem with players who are new to the game and inadvertantly have poor card etiquette, but all of the above were done by people who shouldve known better.]

I hate people that show only one card. I have position so on the showdown they show the ace and i flip over my two pair and then he flips over his other cards which makes a higher two pair. In live games, I have made it a rule that if you show one card, you are mucking the other. When exposing you cards i think it is up to u on what you have to do.