First thing that came to mind.
But it’s certainly my favorite Kiss song. Not that I’m much of a Kiss fan.
“Solsbury Hill” from Peter Gabriel’s first album is totally out of sync with the rest of the album. On the other hand, so is every other track on the album. 
The Bonzo Dog Band’s “I Want to Be with You” is not only out of sync with the album it’s on (Keynsham), but also out of sync with the band’s entire output, and the output of songwriter Neil Innes. It’s a straight pop love song from a band that never wrote a serious song before or (in the case of Innes) since.
“Supersucker Driveby Blues” is at the end of the Supersuckers’ “country” record. It starts out with a little acoustic blues guitar, then slams the pedal to the metal with very loud electric guitar, drums and bass for the next 2 minutes or so. It is quite an out of left field masterpiece. (It’s about giving people the finger and laughing at them when they have car trouble. Real humanitarian stuff.)
I’m gonna go with Only Women Bleed, from Alice Cooper’s Welcome To My Nightmare.
mmm
It was on “The Serpent Is Rising”, and the OTHER side concluded with the “Hallelujah Chorus”, with the pipe organ being played by Dennis DeYoung.
The stranglers’ sublime “Golden Brown” doesn’t really fit in with anything else they ever did.
The last track on London Calling seems very out of place compared to the rest of the album. In fact, it was not until many years later, perhaps as late as Annie Lennox’ cover on Medusa, that I found out that it even had a title.
“Planet Caravan” on Black Sabbath’s Paranoid album. When I was in high school and only had it on cassette, I hated having to either sit through it, or try to fast forward far enough without going too far into the next song.
I love Genesis’ Selling England by the pound, a prog rock masterpiece.
The track More fool me is a hideous simple ballad though.
Sugar Ray’s “Fly” was completely different than anything on their 1997 album*, which was more hard rock/metal. So different that because of the success of Fly, the band’s subsequent albums were all more pop-rock music similar to “Fly”.
*I was duped, and bought the album based solely on hearing the song Fly.
I’ve always thought that “Damned If I Do” by The Alan Parsons Project really sounds like it should be on their album I Robot, from two years earlier, and not Eve.
I always thought “You’re Gonna Make Me Lonsesome When You Go” on Blood On The Tracks was a bit out of sync with the rest of the album. Everything else was a bit on the moody if not dark side and you get this little bit of joy thrown in there.
The Randy Rhoads’ penned “Dee” on Ozzy Osbourne’s solo debut Blizzard of Ozz. A sweet acoustic guitar instrumental in the midst of Osbourne’s and Rhoads’ usual sonic attack (“Crazy Train”, “I Don’t Know”, “Suicide Solution”, etc.).
“I’ll Be Your Baby Tonight” on John Wesley Harding by Dylan. Seems like more of a preview of Nashville Skyline than something that belonged there. Similarly,
“Restless Farewell,” the last track on Times They Are a Changin’, seems more in tune with the next album, Another Side of Bob Dylan.
Also, “On Horseback,” which is at the end of side 2 of Mike Oldfield’s Ommadawn, is a nice simple song not at all like the pyrotechnics of the rest of the album. The Sailors Hornpipe at the end of Tubular Bells is also a bit different, but less. Now the drunken stomp with Viv Stanshell at the end of the first release of Tubular Bells is even more different, but that is not on the most common version of the album.
I’ll nominate “Flood” by Jars of Clay. It’s not just out of place on that album, but it’s the only good song Jars of Clay ever performed*. I guess I should thank Adrian Belew of King Crimson fame for giving them a hand.
*Yes, I know the Contemporary Christian Music scene disagrees with me about Jars of Clay, but if I say more, I should probably take it to the pit.
That’s what I came in to say. But that was a great song nonetheless.
“Mother” on the Police’s Synchronicity.
I always liked that song. It’s not out of place on an LP with folk influences. Why is it 'hideous"?