It is a recreational gun that one loads with rolled up t-shirts as ammunition. It is used to shoot promotional shirts at groups of people. T-shirts usually unfold when landing. It's impact is generally harmless and does not cause injury to the target.
It has a plastic transparent orange tube, where the t-shirts are loaded. It has a navy blue handle, along with a trigger.
This was then later used by Steven to shoot shirts adorned with Buck's childhood drawing at Mayor Dewey and others at an event, causing panic.
It can be seen on one of Steven's shelves that's located above his sofa in his Beach House.
- In "Laser Light Cannon", it contained a shirt reading 'Buy T-Shirt Cannons'. This may imply Greg had not previously used it.