The PC version of one of the best games out there. Fallout 3 is a worthy successor to the classic Fallout PC games, with an update from the top-down turn-based strategy game to a first person-shooter, but this change really works.
Fallout 3 takes place in a dark post-nuclear holocaust world. After having been born in a Vault in the greater Washington DC area, a self-contained shelter whose inhabitants have lived there for hundreds of years, you leave the Vault in order to search for your father. Many varied and extensive adventures ensue, and you are given many opportunities to either help or hurt the inhabitants of the Wasteland you find outside the massive Vault door.
The Wasteland is vast. Many different factions have sprung forth from the ashes of the Capital area, and you must negotiate the factions while battling mutants and giant monsters who have been affected by the incredible radiation caused by the nuclear war.
As your character matures and gains experience, you are able to enhance yourself through various enhancements to aid you. (Among them, I highly recommend Bloody Mess, if only for the ability to watch every enemy explode into unrecognizable parts... fun!) The weapons are quite varied, and you can decide how you want to best equip yourself for the horrors that await you.
While incredibly dark, Fallout 3 retains much of the humor that brought levity to the original series. The war happened while the US was in a period resembling the 1950s, and happy blonde caricatures are ubiquitous throughout the Wasteland offering various advice such as how best to choose a gun to thoroughly decimate your enemy. The soundtrack is filled with many older period pieces, including those by the immortal Ink Spots, as well as one of my favorites, "Let's Go Sunning," originally from a 1954 nudist film. Classic.
The game is supported by 5 DLC packs, each of which adds a lot to the mythology of the world. The value of each is dependent upon the particular gamer, but I found each to be incredibly enjoyable.
As far as achievements, they are incredibly diverse, and rather simple. If you play through the entire game, it will be difficult to miss these. (You should pay attention to the karma ones, though, since if you miss them it will be difficult to go back. Make save games beforehand.) Also, as a bonus to the PC version, there's a little trick to the achievements... I'll leave it to you to discover what that is.
In all, Fallout 3 is a game that will suck you in for several days at least, and will haunt you well afterward. Absolutely recommended without reservation.