Quack

There was once a duck with a gammy eye,
He liked to say Quack,
Nothing rhymes with Quack.
Except
Black
Slack
Back
Track
Crack
Smack
Pack
Jack
Tack
Clack
Hack
Lack
Mack
Sack
Zack
Yak
Whack
I guess lots of words rhyme with Quack
Which is what the duck says