Jason Voorhees

First Appearance: Friday the 13th Part 2 (1981)

The supposed "Drowned as a child" Jason Voorhees isn't happy that a bunch of camp councillors killed his crazy mom and embarks on an epic quest to rid the world of teens who are into sex, drugs, drinking and dancing to terrible music. After hunting down the girl he saw decapitate his mom he realizes it's probably easier to just hang around in the woods near the campground where he "drowned" and his mom was killed, and wait for victims to just come to him.

Yeah I know Jason doesn't get the hockey mask until the 3d-rd movie but I like him better in the mask.
Interesting bit of trivia, Friday the 13th part 6: Jason Lives is the best reviewed of the series and is widely considered the fan favourite even though it performed the worst at the box office and, unlike any other chapter in the franchise, features no on-screen nudity.

Leatherface

First appearance: The Texas Chainsaw Massacre (1974)

A group of annoying kids run afoul of a Texas family with a strange BBQ recipe. Screaming ensues. There's really not much more to the plot than that.

Some folk consider it a classic of the genre, sadly I'm not one of those people. I prefer the later entries in the series. Although I don't think you are supposed to Enjoy Texas Chainsaw Massacre so in that case it might be the most effective of the Chainsaw flicks.
The franchise has become one of the most convoluted of the Classic Slasher Franchises (Halloween, Friday the 13th, Nightmare on Elm Street, Child's Play) with numerous restarts prequels and remakes. This is how the franchise looks as of August 22, 2014:

• The Texas Chainsaw Massacre (1974)
• The Texas Chainsaw Massacre 2 (1986)
• Leatherface: The Texas Chainsaw Massacre III (1990), considering the end of Chainsaw 2 this could be a reboot although it does have a 3 in the title...
• The Texas Chainsaw Massacre: The Next Generation (1994) Probably a reboot, the only character from the first one in this is Leatherface although he behaves a little differently than in the previous movies and there doesn't seem to be any cannibalism.  It stars Matthew McConaughey and Renée Zellweger. It's got a weird Illuminati storyline explaining that maybe the Sawyers are controlled by some kind of shadowy organization. I like to pretend that McConaughey's character in True Detective is the same guy he plays in this movie only here he's in deep cover and that's why Rust Cole so conspiracy minded in TD. But I digress...
• The Texas Chainsaw Massacre (2003) The first "for sure" remake. They change the name of the family for some reason.
• The Texas Chainsaw Massacre: The Beginning (2006) The Prequel to the remake
• Texas Chainsaw 3-D (2013) Claims to be a direct sequel to the original 1974 The Texas Chainsaw Massacre which I guess ignores the original Texas Chainsaw Massacre 2?
• Leatherface: The Texas Chainsaw Massacre Prequel (201X) just announced prequel to the 1974 The Texas Chainsaw Massacre, not to be confused with Letherface: The Texas Chainsaw Massacre III or The Texas Chainsaw Massacre: The Beginning or The Texas Chainsaw Massacre: The Next Generation.

They've recently released a cleaned up version of the film in theatres. I've seen it and although I'm not a fan of the film, it is the best looking and sounding the movie has ever been.

Pinhead

First appearance: Hellraiser (1987)

Since this is the second time I'm writing about Hellraiser (See my entry on Frank Cotton, the real bad guy in the first Hellraiser movie), I'm going to, instead give the synopsis for Hellbound: Hellraiser 2. Or as I like to call it; Hellraiser 2: Hellraiser too.

A few years after the events of the first film, Kristy Cotton finds herself committed to the Channard Institute for weird mental problems, due to nobody believing her story about her uncle Frank getting killed by weird fetish enthusiasts from hell, who travel the world rewarding people who solve their weird puzzle box that's usually delivered by a dirty homeless guy who in reality is a giant bone dragon, with death. Eventually the Lament Configuration gets opened everyone goes to hell and get to meet Pinhead's boss. Once again Pinhead and Kristy meet up. Once again Kristy convinces Pinhead not to kill her but instead to team up with her to fight the real bad guys, or something.
If you haven't seen any of the Hellraiser movies and want to save some time you could start your journey with this movie. It feels like almost half the film's runtime is taken up with footage from the first Hellraiser which is why I call this one Hellraiser 2: Hellraiser too. This doubling of the title also fits as for some reason many of the characters tend to say the same thing more than once, which is why I like to call this movie Hellraiser Too: Hellraiser 2. I think I might have liked this one better than the first one. 

The Baron

First appearance: Manborg (2011)

A soldier is killed during the Hell Wars and is brought back to life in Mega Death City in the future as man kind's only hope (?), MANBORG! Together with #1 Man, Justice and Mina he faces Count Draculon's weird forces in gladiatorial combat until he tires of those "shenanigrams" and brings the fight to Count Draculon himself!

Made for about $1,000, every cent of which show's on screen, the movie is crazy ambitious and extremely fun. Sure it looks like it was made for a thousand bucks but its a million times more fun than half the recent big budget movies I've seen lately. If only all the micro-budget film makers had the kind of imagination and talent the Aston-6 guys.
Oh, and it's a Canadian flick too. Why can't we make more stuff like this in Canada?
I watched twice in a row after blind buying the DVD. I recommend this flick highly.

Michael Myers

Fist Appearance: Halloween (1978)

One Halloween, Little Mikey Myers dresses as a clown and kills his older sister. he spends the next 15 years in a mental institution staring at a wall waiting for October 30, 1978 to take a drive to his home town of Haddonfield, Illinois and teach some babysitters to do a better job of baby sitting. His Psychiatrist knew this was going to happen but still couldn't stop him.
I like to revisit this series every Halloween. Once every couple of Halloweens, I'll watch the entire franchise in one sitting, it pretty much takes all day.
Rob Zombie eventually tried his hand at remaking Halloween. It wasn't terrible but he decided to focus on what makes Michael tick. This had the unfortunate side effect of making him a little less scary.
This is the second time I've tackled Mr. Myers for this series. Since he's probably my favorite of the classic slashers, it probably won't be the last time.

Ahab

First appearance: Father's Day (2011)

A priest, a Backwoods syrup manufacturer (Ahab) with a terrible past (he was framed for killing a man he thought was the "Father's Day Killer") and a young male prostitute (his father was burned to death in front of him by the "Father's Day Killer") embark on an epic quest for vengeance on the man known as the "Father's Day" killer. But is there more to the "Father's Day Killer" than meets the eye?
This is a dark, dark comedy that you probably won't want to watch with your parents or someone you just met. Definitely not a first date movie.
Not to be confused with the Robin Williams movie.

Dr. Peyton Westlake

First appearance: Darkman (1990)
Scientist Dr. Peyton Westlake seeks vengence after being blown up by vicious criminal and amateur finger collector Robert G. Durrant. Unfortunately being blown up has resulted in Dr. Westlake being hideously scarred and losing the ability to feel pain.
Fortunately Dr. Westlake was working on a formula for artificial skin allowing him to make realistic looking masks to disguise himself as anyone. He uses his new found abilities to destroy Durrant's gang and hunt down the man who hired Durrant to blow him up!
This is Sam Raimi's tribute to weird pulpy comic books and the old Universal Monsters.