I was cleaning my bathroom over the weekend, and one of my favorite Shel Silverstein poems popped into my head…I’m pretty sure it’s entitled The Hat:
Teddy said it was a hat,
So I put it on.
Now Dad is saying
“Where the heck’s the toilet plunger gone?”
That never fails to tickle me.
So…what’s your favorite? 
My memory is failing me, but IIRC there was one about someone diving into an empty pool. It had had something about “the most twistable turnable” in it, but I don’t remember if that was describing the dive or the diver.
Anyway that was my favorite.
Off to Google!
A Boy Named Sue
Gotta be “Sarah Cynthia Sylvia Stout Would Not Take the Garbage Out.” I once held a roomful of first graders spellbound with that one. When I got to the line:
At last the garbage reached so high
That finally it touched the sky
One little boy whispered, "Wowwww…"
My favorite is not a poem, but one page of Uncle Shelby’s ABZ Book:
E.
E is for Ernie.
Ernie is the genie who lives in the ceiling.
E is also for egg. Ernie loves eggs!
So go into the kitchen and get a nice fresh egg and throw it as hard as you can at the ceiling and yell: “Catch Ernie, catch the egg!”
And Ernie will lean down out of the ceiling and catch the egg.
(From memory, so may not be exact.)
Biffy, I love that one!! There was another one in that book (I think it’s Where The Sidewalk Ends) about a girl who was faking sick, listing a litany of ailments she had, until she found out it was Saturday and there was no school. Classic!
There’s too many kids in this tub,
There’s too many elbows to scrub,
I just washed a behind,
That I’m sure wasn’t mine,
There’s too many kids in this tub!
That one’s not my all time favorite, but I had to memorize a poem for a 4th grade assignment MANY years ago, and that was it.
My favorite may be the one about the dancing pants. My fifth grade teacher used to read it to us and she would get the giggles so bad every time that she could barely finish it.
My all-time favorites, no doubt, are
“We can’t find the cat-
we don’t know where it’s at-
Oh where did it go?
Does anyone know?
Let’s ask this walking hat.”
And of course,
“I will not play at tug-o-wars-
I’d rather play at hug-o-wars
where everyone hugs, instead of tugs
and everyone giggles and rolls on the rugs
and everyone tickles
and everyone grins
and everyone snuggles
and everyone- wins.”
Merla
My beard grows to my toes
I never wears no clothes
I wraps my hair around my bare
And down the road I goes.
Poor grammar, lovely meter, fun to recite over and over.
My favorite one was next to the light switch in the library. I can’t remember it exactly, but it goes something like:
“Oh no! What do I do?
This library book is one-hundred-forty years overdue!”
Wow, I haven’t spelled numbers in so long that I’m not even sure if that’s how you spell forty. Or is it fourty? I’m pretty sure the first one is right.
At any rate, the poem continues on as the person debates whether or not he should return it and face the long fines or keep it even longer. It’s great.
For Sale
One sister for sale!
One sister for sale!
One crying and spying young sister for sale!
…
Do I hear a dollar?
A nickle?
A penny?
…
My older brother likes to recite it to me on a regular basis.
My absolute favorite, had I to pick one, would have to be “Sick”. But I’m also quite fond of “Band-Aids” (reciting all of the body parts with band-aids on them, in case he should ever get a cut), the afore-mentioned “Sarah Cynthia Sylvia Stout”, “The Unicorn” (about how the loveliest of all, the Unicorn, got left off the Ark), and “Sister for Sale” (which is about exactly what it sounds like).
Oh, yeah, and “Pancakes”, and “The Walrus got Braces”, and “Drats”, and “Somebody Ate the Baby”, and “I’m Being Swallowed by a Boa Constrictor”, and “True Story”, and…
The one about the dog with a tail at either end. (“Though he’s not so good at knowing just exactly where he’s going, he is very very good at sitting down.”)
World Eater:
That is my favorite poemby Shel Silverstein, called The Twistable Turnable Man. When I was a kid, I had that poem memorized and I could say it in under 15 seconds flat. It was the typical kiddie trick that my parents would always have me do at family things. My mom got the biggest kick out of it. However, I don’t remember it having anything about a pool. It was just a non-sensical poem about a man who could twist and turn about.
Another one of my favorites is the title poem in Where The Sidewalk Ends. And another one of my favorites is one called Invitation, which starts w/ "If you are a dreamer, come in/ If you are a dreamer, a wisher, a liar…You get the point.
I could go on and on about Shel Silverstein, but sadly, I am a slow typist, and many years would pass before I could do him justice. 
There’s also “Stacy Brown has Two.” 
Would that, by any chance, be because you’re only one inch tall?
I’ve always liked this one…
Now I lay me down to sleep,
I pray the Lord my soul to keep.
And if I die before I wake,
I pray the Lord my toys to break:
So none of the other kids can use 'em.
Amen
Come in
If you are a dreamer, come in
If you are a dreamer, a wisher, a liar
A hoper, a pray-er, a magic bean buyer
If you’re a pretender, come sit by my fire
For we have some flax-golden tales to spin
Come in, come in.
Also, Listen to the MUSTN’TS, I’m writing this poem from inside a lion, the one about the crocodile’s tooth and I’m being eaten by a boa constrictor.
That one immediately came to mind, but so many other good ones have been posted. I like the Silvia Cynthia Stout one, and also the “My dad gave me a dollar bill, 'cause I’m his smartest son” one, though it’s more of a story than a poem.
Thanks to the OP for stirring a fond childhood memory.
The Smoke-off
Thank you, Dr Demento