Animals
As sly as a fox
Cunning
Sell like hotcakes
Sell quickly
Come rain or shine
No matter what
Six feet under
Dead and buried
Go against the grain
Be unconventional
The lion's share
The larger/largest portion
Don't just accept credulously
Throw caution to the wind
On cloud nine
Blissfully happy
Go down in flames
Fail spectacularly
Like a moth to a flame
Drawn uncontrollably to dangery
Hard nut to crack
Someone/something difficult
Save for a rainy day
Save in preparation for future problems
The whole nine yards
Going truly all out
Go for broke
Risk absolutely everything
A wolf in sheep's clothing
Someone dangerous pretending to be harmless
The way the cookie crumbles
Accepting fate
Fair-weather friend
A friend who won't be there for you in hard times
Catch forty winks
Take a quick nap
Go the way of the dodo
Become extinct or obsolete
The bees knees
Excellent
Full of beans
Energetic
A storm in a teacup
Unnecessary drama
Three sheets to the wind
To be very drunk
Go to the dogs
Decline in quality