"You Never Give Me Your Money" (The Beatles)

When it comes to The Beatles and songwriting, I've always been more of a John Lennon fan.  But it was never really a conscious "Lennon vs. Paul McCartney vs. George Harrison" kind of thing.  I just always liked the quirkier, snarkier, R&B-tinged numbers on my mom's Beatles records, and 90% of those songs just happened to be written primarily by Lennon.
McCartney's "You Never Give Me Your Money" from Abbey Road (1969) is one of a few exceptions, though.
If you're familiar with the album, you know the track is the starting point for the lengthy 8-song medley that comprises most of the album's second side.  But it's more than just a transition piece or bookend for the medley; it's a smart, funky mini-suite featuring one of McCartney's best-ever hooks that concisely summarizes the history of the Beatles up to that point.
Despite public perception that The Beatles were wealthy beyond belief, they actually were bleeding cash following the death of their original manager, Brian Epstein, in 1967.  So they brought on a new financial manager, Allen Klein—a hard-nosed American businessman who also managed The Rolling Stones in the 60s (and screwed Mick & Keef out of the rights to their back catalog).  McCartney wasn't a fan of Klein from the start and felt that his tactics were a little too smoke and mirrors.  
In short, the song opens with McCartney expressing his frustration with Klein always presenting them with vague financial statements on paper instead of actually showing them where the money was.  Hence the line: You never give me your money / You only give me your funny paper.
From there, he reminisces about "the good ol' days" when they were just getting started—no money, no obligations, and no managers, and then shuttles back to the present through a dizzying series of key changes, essentially thanking his new wife Linda for extricating him from the hell of business meetings and whisking him away to the countryside (Step on the gas and wipe that tear away).
Apart from it being a strong track lyrically, the song is one of the tightest final performances of the entire band together.  McCartney treats us to some damn fine boogie-woogie piano and his baritone "Elvis voice," à la "Lady Madonna," not to mention his inimitable melodic/rhythmic bass playing (especially on the 1-2-3-4-5-6-7 / All good children go to heaven coda).  But then there's also Lennon's raunchy distorted guitar, Harrison's bell-like guitar (fed through a rotating Leslie speaker), and Ringo Starr's simple but effective drumming, which punches and punctuates at all the right times.
Most bands don't sound this good when they're at the peak of their powers, much less when they're imploding.