I've found that, on posts I vote to close, the top reason I vote to close is that they are shopping recommendation questions. There is no shopping recommendation pre-canned selection, though, so I usually wind up selecting "life questions" because I feel that the line "what project to start next" is most similar to "where can I buy X".
I think that a specific shopping recommendation tag would make it more clear that they are not allowed because it would show up in the admin tag when the question gets put on hold.