If your deck runs heavy on expensive attachments, the General Store is a must-have.
It's a solid deed in general - it's cheap, has production and control, and has a really good ability. Any ghost rock saved on an attachment can be spent on more dudes, deeds, or (if you're in a hurry to equip them all) other attachments.
The italic help text actually confuses things when it comes to one of the best things about this card. Because it's attaching a goods or spell via a card effect, you can use this deed to attach things to dudes in locations you don't control, and also to booted dudes. For example, you've got town square locked down and really want to give your big bullet stud a Shotgun. However you don't want to risk moving them to a deed to attach it because you think your opponent has been waiting for an opportunity to run a job. General Store lets you attach the Shotgun without needing to move your dude.