The leaked Half-Life 2 beta is an old, old story - and how it happened, and what happened next was documented masterfully by RPS chum Simon Parking a few years back - but a recent fan compilation of all the characters in it who never turned up in the finished article is fascinating. This is the Half-Life 2 that never was, and yet, to some extent, it does exist after all.
That Grayson chap - rings a bell - over on Kotaku ran this video earlier today, in which a YouTube ShoutymanTM does a rapid run through of all the NPCs who never ultimately made it City 17. As with the notorious hydra creature, it's fascinating to see what such a landmark game might have been. There's an alternate, evil Eli, a different Daddy Vance entirely, a faction of Combine sympathisers, and a chap called The Consul who did the Dr Breen thing before Dr Breen was created. City 17 isn't quite as we know it either. To some extent it's more grimdark, but sections of it also seem closer to HL1 than HL2-actual was.
This is games archeology, and I would be entirely happy to see more of it happen. Give me unfinished, discarded Deus Ex maps, half-finished Dungeon Keeper creatures, X-COM enemies based on unused concept art.
Inevitably, modders have been making something out of these Valvian offcuts, which are relatively easily added to Garry's Mod.