a bitter pill to swallow
a hot potato
a sandwich short of a picnic
Achilles' heel
all thumbs
apple of discord
barking up the wrong tree
basket case
bird brain
bite the dust
chink in one's armor
cold shoulder
couch potato
gone south
kick the bucket
rock the boat
sleep with the fishes
take with a grain of salt
throw under the bus
under the weather
wild goose chase