Endgame (Black Mesa)
Half-Life version, see this page.
Endgame is the nineteenth and final chapter of 
Black Mesa. Here, Gordon Freeman is confronted by the G-Man. Both are transported to various locales around Xen while the G-Man praises Gordon's actions there. He explains that his "employers" are now in control of the borderworld for the time being and have authorized him to offer Gordon a job, agreeing that he has "limitless potential".
The final teleportation places them inside a tram identical to the one Gordon rode on at the beginning of the game that is flying through space at immense speed. Gordon accepts this offer by stepping through a portal and hears the G-Man's voice one last time: "Wisely done, Mr. Freeman, I will see you up ahead."
Alternatively, the player may choose not to step into the portal in the final scene. This causes Gordon to be teleported into a giant cave facing rows of Alien Grunts and Alien Crafts as the game ends with the G-Man's comment, "Well, it looks like we won't be working together. No regrets, Mr. Freeman."
Maps
The following .bsp comprises this chapter.
- bm_c5a1a