Locations of the G-Man:
1. Point Insertation: Talking to you before you get in train.
2. "A Red Letter Day": On Kleiner' monitor.
3. Route Kanal: In the Citizen's
Boxcar's TV.
4.
Water Hazard: On the pier of Station 7.
5. Water Hazard: On the broken Combine monitor.
6. Water Hazard: On the bocany at the second level with the
Airboat's cannon.
7. Water Hazard: After the Chopper battle, on the way to the dam control.
8. "We Don't Go To Ravenholm...": Behind some train cars.
9. Highway 17: Threw the Combine Scope at the second house with the thumper, seen talking to Odessa Cubbage.
10. Nova Prospkt: On the first Combine security monitor, flip the swich 2 times.
11. Adicitizen One: On the TV in the destroyed familer building.
12. Adicitizen One: On the monitor the Citizens are pulling down.
13. Dark Energy: Talking to you after portal got destroyed.
14. Undue Alarm: Captured by the Vortigaunts.
15. This Vorial Coil: Talking to you, while
Vorts heal Alyx.
16. Freeman
Phonex: On the bridge at the second level.
17. Under The Radar: Going inside White Forest Inn.
18. Our Mentel Feind: On the monitor where
Mossman's video held.
(That is it intill Episode Three)