When I (or someone on my server) equips the Sydney Sleeper, we only see a missing texture across our screen. When we equip the Shooting Star, it goes away but when we switch to something else again it comes back. We have TF2 mounted onto gmod.
EDIT: It gets fixed when we go into Post Process and turn one of the effects/shaders or something like that and then turn it back off.
Then when we switch to a different weapon, any weapon at all, it comes back.