Barney Calhoun is a playable character in Half-Life: Blue Shift, and a major character in Half-Life 2 as well as Episode One. Starting out as a security guard at Black Mesa Research Facility, he eventually joins the Lambda Resistance and works as a mole in the Combine Civil Protection Forces.
In Half-Life 2, Alyx Vance is a brilliant hacker and mechanic who is a close friend of Gordon Freeman. She helps Gordon by providing weapons and fighting alongside him. She owns a robot named “Dog”, which she built herself.
Gnome Chompski is a garden gnome who likes to make unlikely appearances in video games, including Half-Life 2, Left 4 Dead 2, and the Final Hours of Portal 2. As far as we can tell, there’s no relation to the famous linguist.