It seems that if a card already is in play that changes Fixer's damage type, and then if Tire Iron enters play after, he'd still just do projectile Damage.
Now, what if Grease Monkey Fist is already in play and then he plays Tire Iron. Is it still just projectile? Or does each Monkey Fist trigger change the Projectile damage to whatever?
You can decide which order these card are applied. So it can be either Projectile or any damage type, which is really the same as any damage type.