“Don’t reveal your hand”
“When the chips are down”
“Don’t put all your cards on the table”
“Put on your poker face”
“I’ve got an ace up my sleeve”
“Ace in the hole”
Any others?
‘Penny ante.’
‘Play your cards close to your chest.’
‘Not playing with a full deck.’
“If I play my cards right…”
“Black as the ace of spades”
'You gotta know when to hold ‘em…’
‘Too rich for my blood.’
“It’s all come up trumps”
“He holds the trump card.”
“Dead man’s hand”
Most likely from bridge:
“has it in spades” (spades being the highest ranking suit at bridge)
“Y is not his strong suit”
“X trumps Y” (meaning that X beats out or takes precedence over Y)
Then there’s also the phrase “go fish” 
About a year ago 2002 World Series of Poker champion Robert Varkonyi wasted a page in Cardplayer Magazine listing off some poker terms that have entered common parlance.
“It’s a push”
“Winner take all”
“pass the buck”
“peg out”
“Holding all the cards”
“Snap!”
I call Tichu
“Deal me in”; “Deal me out”
“Uno!” I hear all the kids in Mexico use that to signify one now.
“The cards are (deck is) stacked against you.”
Just thought of another one:
“He was dealt a bad hand in life.”
He’s holding the nuts.