Cash Landrum Incident. Allagash Abduction. Latter case was later debunked though.

Here we go I found it easier than I thought I could.
http://unsolved.com/archives/don-henry-kevin-ives

The main one I've never forgotten was the two boy who were out night hunting and ran over by the train. They were seen laying next to each other on a train track covered by a tarp. I've always remembered this one the best when ever I think of the show.
I recently saw this again streaming on Amazon. I looked it up and saw it hasn't been solved. But on one of the Unsolved websites people replied about the case and many accused the Clintons. Bill was governor at the time and people who lived in the area said he was part of the drug problem there. I'm on my phone so I can't link anyone to this but maybe someone else can. I found it interesting reading what others had to say.

Bill & Dorothy Wacker - Elderly couple terrorised in their home for a number of years.
Sneha Philip - Woman disappears on September 10th, 2001 near the World Trade Center
Keith Reinhard - The writer/store owner who disappeared while writing a novel about Tom Young's disappearance.
Jim Kimball - Boy with mental illness that disappeared.

The Queen Mary Ghosts Segment.
I saw it when it originally aired on the Halloween Special. It was released on the Ghosts DVD set, which I know have.
They showed many of these ghosts sitting in chairs, and standing behind people But they were in still poses like mannequins and had zombie like expressions on their faces.
Many Many other stories were great too
But it was the unique portrayal of these ghosts, that I remember most. It has always creeped me out since the first time I saw it.
The evil laugh of the pool girl ghost was creepy too
By The Way, that EVP they caught in the bow was very interesting
Did anyone notice the "Great Skeptic" Dr. William Roll, couldn't "debunk" it, like he usually tried to do with almost every other case that Unsolved Mysteries brought to him
"
Oh This haunting was caused by bedrock stones rubbing together, and created magnetic fields which affected the minds of the homeowners causing them to hear banging on the walls of their home, and caused the little girl to see a man pushing her on her swing.
"
Oh Please Do you really expect us to always believe that same exact lame excuse?

The episode where a guy on a motorcycle gets hit in the back of the head by a 2x4 from someone in a pickup truck. He was killed and iseemed to be a random act of violence.

The most memorable cases are unexplained deaths or disappearances. 1) The Kerstetter disappearance from the factory in very rural, isolated northwestern Pennsylvania stands out. 2) The young woman who disappeared from a bank after reading graffiti apparently meant for her at the end of the block. 3) The premiere story about the deserted Wyoming intersection with the running truck and driver missing from the wheel.
The most frightening of any Unsolved Mystery show, ever, was the pregnant woman almost abducted and killed by the New Hampshire serial killer, who speeds off toward safety only to realize she is tailing the serial killer.

http://unsolvedmysteries.wikia.com/wiki/Brad_Bishop
A man murders his whole family and then disappears without a trace. This one is really freaky.
I've often wondered if this killer had friends in extremely high places. That chance meeting in the men's room was twenty years before the internet, I know.

It's tough to choose, but a few that I remember all these years later are:
http://unsolvedmysteries.wikia.com/wiki/Betty_Cash_and_Vickie_Landrum
A family sees a U.F.O. and later suffer radiation-related illnesses.
http://unsolvedmysteries.wikia.com/wiki/Bobbi_Oberholtzer_and_Annette_Schnee
Two young women are found murdered several miles and six months apart, but a pair of orange socks links them.
http://unsolvedmysteries.wikia.com/wiki/Stockton_Arsonist
Some people find a discarded video cassette. When they take it home and watch it, it's of a burning house and the person taping it is uttering all kinds of satanic stuff.
http://unsolvedmysteries.wikia.com/wiki/Bill_and_Dorothy_Wacker
A elderly couple is terrorized in their home over several years.
http://unsolvedmysteries.wikia.com/wiki/Brad_Bishop
A man murders his whole family and then disappears without a trace. This one is really freaky.

http://unsolvedmysteries.wikia.com/wiki/Russell_Evans
Tragic and a mystery.
http://unsolvedmysteries.wikia.com/wiki/Bill_and_Dorothy_Wacker
Hilarius and strange.

The Chupacabra case for sure. My friend and I had nightmares!

Tough to choose, since they all mean something to the people involved, but the Halloween/Ghost themed episode that aired in 1988 aboard the Queen Mary is certainly memorable, with four classic cases, which can be seen on the DVD set called
Ghosts
.