G-ManEditThe man with a plan, the mutual friend, the illusive character behind the curtains, appearing throughout the series, following, watching, and sometimes helping (or hindering) some characters.
He appeared in all of the official Half Life games so far (Half-Life and Source remake, Opposing Force, Blue Shift, Half-Life 2 and Episodes 1 and 2, and Decay), but he also appears in some mods, following other "interesting persons".
-Sweet Half Life (stalked by McGinley in the ending).
-The Citizen Part 1 and 2 (following and saving the main character).
-Joutomaa (following, saving, and advising the main character).
The G-Man is also killed in some mods, which is impossible to do in the official series:
-Peaces Like Us (disintegrated by a giant green ray).
-Todesangst 2 (transformed into humanoid monster and shot down).
-Coastline to Atmosphere (shot down by Freeman and vaporized in the space station's explosion).
-Timeline 3: Heart of Darkness (disappeared in sprites when the space dimensional crystal is destroyed).
Some mod's can also make an identity for G-Man, or re-skin his model :
-G-Man is known as Mr. Blackstone in Todesangst.
-He has many clones of him supervising the universe in Fate Reversal.
-He is re-skinned as the Sheriff in the They Hunger series.
-He is re-skinned as Adolf Hitler in Timeline series.