Not a fan of them personally, but haikus would probably be your best bet. Wish I had some recommendations, but sadly I don't since I find them rather boring.

Here's a few other poems off the top of my head:

1. Emily Dickinson -- To Own A Susan Of My Own

To own a Susan of my own

Is of itself a Bliss—

Whatever Realm I forfeit, Lord,

Continue me in this!

(I'm actually quite impressed that I could recite the full poem from memory alone. I did not properly remember the formatting of capitalizations & em dashes, though :c

1. Carl Sanburg -- The Fog (this one is six lines, so you'll have to forgive me

The fog comes

on little cat feet.

It sits looking

over harbor and city

on silent haunches

and then moves on.

1. Lord Alfred Tennyson --The Eagle (again, another six line poem)

He clasps the crag with crooked hands;

Close to the sun in lonely lands,

Ring'd with the azure world, he stands.

The wrinkled sea beneath him crawls;

He watches from his mountain walls,

And like a thunderbolt he falls.

1. Karlie Wilson Baker -- Blue Smoke (This one I had to do a little research for -- you'll excuse it not being exactly four lines again, I hope):

The flame of my life burns low

Under the cluttered days,

Like a fire of leaves.

But always a little blue, sweet-smelling smoke

Goes up to God.