When Obsidian took over from BioWare to develop Knights of the Old Republic II, the game was famously (and forcibly, by Lucasarts) shipped "incomplete". Only when modders reinstated a bunch of cut content could we enjoy the full experience the developers had planned for the game.
Much the same happened when the studio took over from Bethesda to handle Fallout 3's follow-up, New Vegas. While nowhere near as critical to the user's enjoyment of the title - KOTOR II's biggest cuts were literally at the end of the game - there's still a bunch of stuff floating around as stray code on the disc that never made it into the finished product.
Modders have been picking at the edges of this for a while now, but this week a user by the name of Moburma collected it all in one spot, outlining where the cuts were made and what they consisted of. Even better, he's made most of them available for download as mods, meaning you can slide them in and enjoy what's basically an extended edition of the game.
UPDATE - To be clear, I'm not implying these cuts were anywhere near as drastic as those in KOTOR II, nor that this is somehow the definitive edition of the game. As the modder explains, much was cut for good reason. What's "much the same" is the fact the cut content is now playable.
Fallout New Vegas Cut Stuff [Cutting Room Floor]
moburma80 [New Vegas Nexus]