Michael Weston and Sam Axe. (And Fiona.)
That’s a good one. Sam is insanely loyal. I spent a good part of last season wishing he’d kick Mike to the curb, in fact, because Mike deserved the ration of shit he was receiving but Sam didn’t.
Han and Chewie
Lucy and Ethel. Ethel would totally take a bullet for Lucy (unfortunately, Lucy would most likely be the one to accidentally fire that gun…)
The Hardy Boys.
The Scooby Doo Gang.
The Thousandth Man
One man in a thousand, Solomon says,
Will stick more close than a brother.
And it’s worth while seeking him half your days
If you find him before the other.
Nine hundred and ninety-nine depend
On what the world sees in you,
But the Thousandth man will stand your friend
With the whole round world agin you.
'Tis neither promise nor prayer nor show
Will settle the finding for 'ee.
Nine hundred and ninety-nine of 'em go
By your looks, or your acts, or your glory.
But if he finds you and you find him.
The rest of the world don’t matter;
For the Thousandth Man will sink or swim
With you in any water.
You can use his purse with no more talk
Than he uses yours for his spendings,
And laugh and meet in your daily walk
As though there had been no lendings.
Nine hundred and ninety-nine of 'em call
For silver and gold in their dealings;
But the Thousandth Man h’s worth 'em all,
Because you can show him your feelings.
His wrong’s your wrong, and his right’s your right,
In season or out of season.
Stand up and back it in all men’s sight –
With that for your only reason!
Nine hundred and ninety-nine can’t bide
The shame or mocking or laughter,
But the Thousandth Man will stand by your side
To the gallows-foot – and after!
Rudyard Kipling
Interesting case. They had nasty fallings out with each other more than once, and all too often found themselves working at cross purposes. Yet, ultimately, they are more than just friends, more even than brothers: they are two halves of a vaster, greater, primordial hero (“The Growler.”)
Were Eng and Chang good friends? In one sense, not at all. In another…the best friends in the whole damn world.
Jed Bartlett and Leo McGarry.
Xena and Gabrielle.
Hercules and Iolaus
Good point. How about Silver Age Batman and Superman?
Kemper Boyd and Ward Littel.
Oh, GOOD call.
Jack Aubrey and Steven Maturin? I haven’t read all the books, so y’all would know better than I.
Buffy, Willow, Xander
Seeing Xander’s real friendship with Buffy grow beyond a crush was a nice surprise.
Oh, they were gay, but unfortunately it was an unrequited love because if they ever had sex, Superman’s sperm would kill poor Batman. 
In all seriousness, they were definitely friends, but if modern viewers were to ever look at the comics from the 50s and the 60s, we’d definitely find all sorts of homoeroticism not intended by the writers.
Sort of like how this scene here, Hollywood’s first onscreen same sex kiss, from an oscar winning film would have modern audiences rolling and laughing at what they saw as homoeroticism, particularly with the “heinie” comment while audiences from the 20s, if they saw modern reactions would be like, “what are those idiots laughing at”.
Mal and Zoe.
In Greek mythology, Damon and Pythias are held up as the model for best friends.
Buzz Lightyear & Woody, at least by the end of TS3
Sulley & Mike Wazowski, Monsters, Inc.
Johnny Storm & Ben Grimm
Turk and J.D.?
They definitely embarrassed themselves for each other.
Captain Aubrey and Stephen Maturin, from a shakey start and a couple of bumps along thier early friendship. They remain, loyal and devoted, both risking life for the friendship.
Mr and Mrs Micawber.
Colonel Newcome and Clive Newcome.
Granny Weatherwax and Nanny Ogg