Gordon Freeman
In "Half-Life: Blue Shift", the playable Barney progresses through Black Mesa to escape the events of the Resonance Cascade and is able to do so, in contrast to Gordon Freeman and Adrian Shephard, who are held in stasis. In "Half-Life 2", Barney works as a mole for the Lambda Resistance in the Combine Civil Protection Forces. He provides the player information in the first chapter, leading him to Kleiner and Vance, and in the end of the second chapter, he provides the player with his crowbar. The fact that Barney owes Gordon Freeman a beer is a running gag in the series.