Un Evil Laugh

BLA HA HA HA HA! No, that doesn't sound right....How about.... KWE HE HE! No, that one makes me sound like a chocobo. I want Cecil to fear me, not laugh at me. Maybe.... FUYA HA HA! *sigh* Golbez made all this look easy.

—The Drab Lord, Captain SNES episode 153

A villainous laugh so remarkably stupid-sounding that, instead of striking fear into the hearts of those who hear it, it causes bouts of uncontrollable sniggering. This may or may not have been done on purpose. Contrast Giggling Villains, whose seemingly unimpressive laughs only make them creepier. Compare Laugh with Me in which the villain demands that someone laugh as well.

Examples of Un Evil Laugh include:

Anime And Manga

Depending on the dub. Light Yagami of Death Note. Some are better than others.
The villain's laugh in the Leiji Matsumoto parody episode of Excel Saga is notably and consistently thick and forced-sounding. At least, it is in the original Japanese.
The Japanese version of Yu-Gi-Oh! gives us Insector Haga (dubbed as Weevil Underwood). Given the character, its likely he was at least trying to be sinister...
KEEERO KERO-KERO-KERO-KERO!
tor..pedotorpedotorpedotorpedotorpedotorpedo!
Considering how many funny laughs there are in One Piece, villainous examples are there.

Comics

Chick Tracts: HAW HAW HAW

Film

In Harry Potter and the Deathly Hallows - Part 2, Ralph Fiennes ruined what would have been an impressive moment of Voldemort gloating over Harry's Disney Death with a bizarre "EH-heh-heh-HEH!!", which sounds so comically awkward you wonder how they even left it in there.
Evil Ed from Fright Night has a voice crackling with pre-puberty, and a laugh like a donkey on inhalants. As a vampire, the laugh gets more reverb, but it's still the same goofy laugh.
Intentionally done in Austin Powers, where Scott Evil's laugh in Goldmember sounds more like a mix between screaming and crying, is incredibly hilarious, and gets him reprimanded by Dr. Evil for doing it wrong. By the end, though, he's learned how to have an effective laugh.
Dr. Flemyng, from The Lost Skeleton of Cadavra. The Skeleton itself has a far more traditional, if hammy, laugh.
From Prince of Space, we have the Phantom's drawn-out, twangy chortle, which sounds like an unholy merger of Burgess Meredith as The Penguin and a car with a bad starter motor. Haaaa-haaaa-haaaa-haaa-haaa-haaa-haaa-haa-haa-haa-haa-haaaa.
Tex Richman in The Muppets and his "maniacal laugh, maniacal laugh, maniacal laugh!" (He's not laughing. He's literally saying that.)

Literature

In one of the A Series of Unfortunate Events books, Count Olaf has begun practicing a bizarre evil laugh that involves interjecting random words that start with the same letter as whatever onomatopoeia for laughter he happens to be using.

Live Action Television

The Count from Sesame Street. "Ah-ah-ah." He did have a more sinister one when he started out, though.
Phoebe and Joey from Friends attempted to laugh evilly after concocting a scheme to bring Ross and Rachel back together. Unfortunately, Joey kills it.

Stand Up Comedy

Achmed, the Dead Terrorist has a less-than-menacing evil laugh, which is usually used to punctuate a particularly offensive joke. By contrast, one of the other puppets, the mean, grouchy old man Walter, has a laugh that scares him.

Video Games

In Kingdom Hearts II, when the surviving members of Organization XIII first appear to the main character, one can clearly hear Demyx's rather uninspired titter among the collection of otherwise decent Evil Laughs.
- In Birth By Sleep (or at least the Japanese version), Vanitas' laugh is even more ridiculous.
Alfred Ashford's...um...interesting laugh in Resident Evil: Code Veronica.
Jak and Daxter parodies this in the outtakes with Gol. "SICKLY. Evil laugh."
In No More Heroes, Destroyman's laugh is a pretty good example, and given the setting probably intentional.
Brady Culture from the adventure game Sam and Max: Culture Shock has a few false starts with his evil laugh before getting it down pat.
In Final Fantasy VII, Heidegger and Scarlet are nicknamed "Gyaha" and "Kyaha" by Cait Sith. Hard to be worried when they're around.
Team Fortress 2, The Spy: "HON HON HON *snort* HON HON HON"
Most of the Laughably Evil villains of the Pokémon Mystery Dungeon games, such as "Chaw-haw-haw!", "Whoa-ho-ho!", and "Heh heh heh!" The more sinister villains will have laughs like "Ooh hoo hoo hoo!", but the most terrifying laugh from those villains would be "MuhehehehehehehehehehehehehehehehahahahahahahahahahahahHAHAHAHAHAHAHAHAHAHAHAHAHAAHAAHAAHAAHAA!!!"
"UWEE HEE HEE!" Monster Clown though he may be Final Fantasy VI's Kefka lacks something in the terrifying laugh department.

Web Comics

In Narbonic, Helen Beta Narbon has a proper evil laugh... which lasts for about three seconds before devolving into giggles, titters, and snorts.
Implied with Xykon in The Order of the Stick. Since his transformation into an undead Lich robbed him of his lungs, he hasn't been able to do a decent Evil Laugh.
Spinnerette's Doctor Universe commented that he often wished his laugh was more maniacal.

Web Original

In Doctor Horribles Sing Along Blog, Dr. Horrible's laugh is like this at first, practicing in front of his webcam with little success (he has a vocal coach). Later on, after he decides to take things up a notch, he finally pulls it off, striking fear into everyone present.
Wayne the goblin in Legendary Frog's "One Ring to Rule them All" series had this when applying for the evil henchman position.

Western Animation

Beautiful Gorgeous from Jimmy Neutron has a giggling, chortling, horrible laughter.
Man dark in Dexters Laboratory: HA haha! HA haha! HA haha haha!
Señor Senior, Junior's laugh in Kim Possible.
- Ron Stoppable gets turned evil in one episode and Shego is noticeably in pain from hearing his "evil laugh" because it's so terrible. Oddly enough, though, he's actually quite dangerous and competent in all other evil areas.
The spastic chortling of Dark Lord Chuckles the Silly Piggy in Dave the Barbarian.
- Dave's evil ex-girlfriend also botched the evil laugh. BWO HO HO HO HO!!! Never goes without being lampshaded.
The Antichrist in the Rapture episode of American Dad.
In Xiaolin Showdown, Jack Spicer's "evil" laugh starts out decent, but ends up being rather pitiful, as he tries too hard.
- Pandabubba is just as bad at this, with a sputtering laugh as silly as Chuckles the Silly Piggy's.
Played with in The Backyardigans episode "Flower Power". Austin, playing the villain The Gloommeister, performs his Evil Laugh. When asked why he laughs like that, he says that it sounds better than his normal one, and then demonstrates—with a giggle-snort that would have made Steve Urkel proud.
During his stint as a car salesman in The Simpsons episode "Diatribe of a Mad Housewife," Homer attempted to do his own evil laugh on what he thought were some unsuspecting customers. He didn't exactly miss any notes, but without any dramatic echo, music, or shadows, it came across as more awkward and silly than outright menacing.