Most of the alternate costumes you can unlock. Going through Silent Hill wearing a Mexican Wrestler outfit or full-body dog suit? Perfect Nightmare Retardant!
The description for the dog suit (called the Daredevil outfit in-game, for the achievement used to unlock it) is also rather funny: "Wearing this makes me feel like top dog."
Alessa normally doesn't express much emotion when she appears to Travis, but after you defeat Caliban, she walks over the dead boss and, still stoic as ever, gives it a firm kick in the head. She did not like that character in the play.
Travis seems at a loss for words when describing the Flauros during his tirade with Alessa, only really able to settle on calling it a "thing" after searching for a term that sounded less like Buffy Speak.
Some of the weapons Travis hurls at enemies are portable televisions and typewriters which he stores in his Hyperspace Arsenal. Watching him try to pick up other things like clues while holding a wine bottle is hilarious.