After eight years in the making and missing deadlines, Black Mesa will finally be released this coming September 14.
Black Mesa is a Source Engine game made as a reboot of the disappointing Half-Life: source. The trailer from 2008 announced that the game will be released in 2009. The team didn't deliver, instead stating a "When it's done" mantra.
Note this is just the first half of the game, and the release date of the second part is left unannounced. Maybe another 8 years?
UPDATE: gameplay of a recent build