Well, there's a surprising lot of them.
Age of Chivalry- Some medieval game with knights.
Alien Swarm- although if you get a certain achievement, you get a special hat in TF2.
Apex Legends- Yes, a game published by EA is on the Source engine.
Dino D-Day- I've never played it (like the rest I mention), it might have something from Day of Defeat, but I could say that with literally any WW2 game on Source.
Fistful of Frags- A Wild West themed game whose title is clearly riffing on a certain movie by Sergio Leone.
And there's definitely a lot more that I can't bother to mention
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Fistful of frags
Postal 3
Well, there's a surprising lot of them. Age of Chivalry- Some medieval game with knights. Alien Swarm- although if you get a certain achievement, you get a special hat in TF2. Apex Legends- Yes, a game published by EA is on the Source engine. Dino D-Day- I've never played it (like the rest I mention), it might have something from Day of Defeat, but I could say that with literally any WW2 game on Source. Fistful of Frags- A Wild West themed game whose title is clearly riffing on a certain movie by Sergio Leone. And there's definitely a lot more that I can't bother to mention