Harry Potter and the Chamber of Secrets (GCN)

Art (Mona Lisa): In the Gryffindor Common Room, near the exit, you can see a "Mona Lisa" picture hanging on the side. (Credit: Deven711)
Status: Unverified

Haunting Starring Polterguy (Genesis)

TV Shows (Casper): After the second level, Poulterguy says "Yeah...and I'm what's-his-face, the friendly ghost", refering to Casper. (Credit: Andy Thorley)
Status: Unverified

Hell: A Cyberpunk Thriller (3DO/PC)

Cross-Series (Bloodnet): The password to Dolph's computer is BLOODNET. This is a reference to a PC game of the same name. When you're given the password, Rachel says something like, "What does Bloodnet mean? That's just an old computer game!"
Status: TRUE: Verified by FO.

Programmers: Here's one that's easy to miss. When you're taken to Asmodeus's studio, there's a brief shot of his Director's Chair. The Take2 company logo is on the back of it, Take2 being the company that made Hell.
Status: TRUE: Verified by FO.

Famous Person (The Rolling Stones): This game has two references to the Rolling Stones. One is when Cynna Stone says that the band played "Satisfaction" too many times at a wedding reception. The other is a character named "Mick" whose face looks like Mick Jagger's.
Status: TRUE: Verified by FO. (I suppose the Mick character reference could be debatable, but I'm still marking it true, because the other mention of the Stones is rock solid.)

Famous Person (Dolph Lundgren): Is the character Dolph named after Dolph Lundgren? Possibly. They're both bodybuilders and Grace Jones, who appears in Hell as the Imperator Solene Solux, once dated him.
Status: Unproven: I don't think it's coincidence, but it could be.

Mythology (Biblical): These ones are so obvious, I almost didn't want to post them. The main character Gideon was most likley named after the Gideon Bible and the character Dante after the author of The Inferno. Also, Asmodeus, Belial, and Beelzebub are all Biblical demons, and Mephistopholes comes from the story of Faust, about a man who sold his soul to the devil.
Status: TRUE: Considering that the game is called "Hell" and deals with the subject of Hell, I seriously doubt ANY of these are coincidence.

Famous Person (Various): I have to mention this one because of how strange it is. Grace Jones plays Imperator Solene Solux and Geoffrey Holder plays Jean St. Mouchoir. Both of these actors have played James Bond villains (Mayday and Baron Samedi), and both appeared as their respective James Bond characters in the N64 game, Goldeneye 007. It's also worth mentioning that Dennis Hopper plays Pazuzu (our favorite Mesopotamian wind demon) and supermodel Stephanie Seymour plays Cynna Stone.
Status: TRUE: Verified by FO.

Hot Shots Golf Fore! (PS2)

Cross-Series (Ratchet & Clank): Ratchet and Clank are unlockable characters. (Credit: Andy Thorley)
Status: Unverified

Hydlide (NES)

Music (Indiana Jones): The theme song is a rip-off of the main Indiana Jones theme, aka "The Raider's March".
Status: TRUE: (Hydlide Theme Midi) proves it. Really, this is just about the most shameless and blatant rip-off of a song I've ever heard. Here is a (Midi) of the real Indiana Jones song for comparison.

HyperZone (SNES)

Console (SNES): The third boss is one-half of a Super Famicom controller.
Status: TRUE: (Screenshot) proves it.

Movie (Star Wars): This game's package and label art is clearly a rip-off of the trench battle in Star Wars. The ship looks like an X-Wing, which is a clue that something is strange here because NO ship in the HyperZone game looks like that! Also, from what you can see of the pilot in the ship, he's wearing Luke's orange and white uniform and helmet. Finally, the ship is flying through a "trench".
Status: TRUE: Verified by FO. Similarities too strong to be coincidence.