I think my favourite has to be "Willie Wastle" for its humour and the pictures it creates -

Willie Wastle dwalt on Tweed,
The spot they ca'd it Linkumdoddie.
Willie was a wabster guid
Could stown a clue wi onie body.
He had a wife was dour and din,
O, Tinkler Maidgie was her mither!
Sic a wife as Willie had,
I wad na gie a button for her.

She has an e'e (she has but ane),
The cat has twa the very colour,
Five rusty teeth, forbye a stump,
A clapper-toungue wad deave a miller;
A whiskin beard about her mou,
Her nose and chin they threaten ither:
Sic a wife as Willie had,
I wad na gie a button for her.

She's bow-hough'd, she's hem-shin'd,
Ae limpin leg a hand-breed shorter;
She's twisted right, she's twisted left,
To balance fair in ilka quarter;
She has a hump upon her breast,
The twin o that upon her shouther:
Sic a wife as Willie had,
I wad na gie a button for her.

Auld baudrans by the ingle sits,
An wi her loof her face a-washin;
But Willie's wife is nae sae trig,
She dights her frunzie wi a hushion;
Her walie nieves like midden-creels,
Her face wad fyle the Logan Water:
Sic a wife as Willie had,
I wad na gie a button for her

But for a romantic poem then "Ae fond kiss" has to be my favourite

Ae fond kiss, and then we sever;
Ae fareweel, and then for ever!
Deep in heart-wrung tears I'll pledge thee,
Warring sighs and groans I'll wage thee.--

Who shall say that Fortune grieves him,
While the star of hope she leave him:
Me, nae chearful twinkle lights me;
Dark despair around benights me.--

I'll ne'er blame my partial fancy,
Naething could resist my Nancy:
But to see her, was to love her;
Love but her, and love for ever.--

Had we never lov'd sae kindly,
Had we never lov'd sae blindly!
Never met--or never parted,
We had ne'er been broken-hearted.--

Fare-thee-weel, thou first and fairest!
Fare-thee-weel, thou best and dearest!
Thine be ilka joy and treasure,
Peace, Enjoyment, Love and Pleasure!--

Ae fond kiss, and then we sever!
Ae fareweel, Alas, for ever!
Deep in heart-wrung tears I'll pledge thee,
Warring sighs and groans I'll wage thee.

And if you like something a bit down to earth then there is "Twa wives"

There was twa wives, and twa witty wives,
As e'er play'd houghmagandie,
And they coost oot, upon a time,
Out o'er a drink o brandy;
Up Maggie rose, and forth she goes,
An she leaves auld Mary flytin,
And she farted by the byre-en'
For she was gaun a shiten.

She farted by the byre-en',
She farted by the stable;
And thick and nimble were her steps
As fast as she was able:
Till at yon dyke-back the hurly brak,
But raxin for some dockins,
The beans and pease cam down her thighs,
And she cackit a' her stockins.