Animal Crossing [N64/GCN]: The game has a series of NES games which can be unlocked through entering codes in Tom Nook's store. However, there are a select few which can only be unlocked through e-reader cards. There is also Animal Island, an island that can only be accessed with a Gameboy Advanced and link cable, which are the only way to get two games and coconuts. The following are NES games which are on disc but need cards or the Gameboy Advanced to be accessed: Wario's Woods, Baseball, Soccer, Donkey Kong Jr., Donkey Kong 3, Clu Clu Land D, Punch Out!!, Mario Bros, Ice Climbers and Super Mario Bros.
Ace Combat 6 [360/PS3]: Dozens of pallette swaps and planes.
Beautiful Katamari : A good portion of the levels are locked on the disc and they require purchase. [NOTE: Katamari Forever contains most of BK's content, including "DLC" content.]
Bioshock 2 [360/PS3/PC]: "Sinclair's Solution", a multiplayer expansion with new maps and loadouts.
Crew, The [Xbox One/360/PS4/PC]: Multiple vehicles, mainly off-road editions of road cars, the most blatant of which being the 1969 Camaro RS, which is featured prominently in two missions and yet is unavailable to the player. As of 03/18/2015, it has yet to be made available.
Bulletstorm [360/PS3/PC]: Six "Echoes" missions (Score Attack / Time Trials) and the "Anarchy Mode" (Multiplayer) require a code to unlock. New copies of the game come bundled with an unlock code, while gamers who buy used copies may have to pay $10 to unlock it.
Dragon's Dogma [360/PS3]: Additional sidequests.
Dynasty Warriors Gundam 2 [360/PS3]: 10 free missions.
Freedom Force [PC]: Shipped with 3 bonus character accessible via a preorder code. Later, Irrational Games released the code to unlock them for everyone.
Ghost Recon: Future Soldier [360/PS3]
King of Fighters XIII [360/PS3]: 3 playable characters: Ex Kyo, Ex Lori, and Mr. Karate.
Metroid Prime [GCN]: The Fusion Suit costume and original NES Metroid game were only unlockable after using a GameCube to GBA link cable and connecting to a copy of Metroid Fusion. [NOTE: The Wii version of New Play Control Metroid Prime and Metroid Prime Trilogy will automatically unlock this content after beating the game once.]
Persona 5 [PS3/PS4]: Every piece of DLC except for the Japanese voiceover is on disc.
Resident Evil 5 [360/PS3/PC]: "Versus" mode was locked. The price to unlock was $5. [NOTE: The Gold Edition of RE5 comes with Versus unlocked already, as well as additional content.]
Resident Evil 6 [360/PS3]: Three maps from "The Mercenaries" mode are locked away. Unlock codes are being given out as pre-order bonuses from specific retailers: Amazon, Best Buy, and GameStop. Each retailer will give you a different map.
Resident Evil: Operation Raccoon City [360/PS3]: Weapons and costumes. Unlock codes came with the "Limited Edition" copies.
Samba de Amigo [Arcade/DC/Wii]: Additional songs could be downloaded or unlocked then played by connecting the Dreamcast to the internet. This is not the case with the Wii release. (The Arcade version lacked this feature)
Saints Row The Third [360/PS3]: 12 DLC packs, including cheats, clothing, vehicles, and weapons.
Soul Calibur IV [360/PS3]: The characters Yoda and Darth Vader are on the discs for both versions of the game, but on the 360 you must pay to unlock Darth Vader, while on the PS3 you must pay to unlock Yoda.
Soul Calibur V [360/PS3]: Dampierre, a playable character, is on the disc for both versions.
Sonic Generations [360/PS3/PC]: Casino Night Zone. A pinball mini-game given to GameStop pre-orders. Available for purchase separately.
Street Fighter X Tekken [360/PS3]: 12 characters, including fan favorites such as Elena, Dudley, Lei, and Bryan Fury. Also, various "Gems" which grant special abilities.
Tekken Tag Tournament 2 [360/PS3]: 4 characters: Kunimitsu, Ogre, Angel, and Michelle. If one pre-orders the game at specific retailers they get one of the characters, while the others will be downloadable down the line. None of them will cost a single cent however, so this on-disc DLC is free.
Ultimate Marvel VS Capcom 3 [360/PS3]: Jill & Shuma. Both cost $10. Costumes are also locked on the disc.
WWE 12 - Playable characters HBK, Jim Ross, Jerry Lawler. Alternate costumes for Edge, Christian, and Road Warriors.