I've mulled this over, discussed it on other forums, and there really isn't much I can come up with.

There's weather related, regional issues first and foremost. Something like Katrina. And I think such a situation depends on getting out of the area before the weather hits, if possible.

Then there's civil un-rest, as in Ferguson. Obviously it's become politically incorrect for LEAs to treat such situations harshly by shooting the first few looters and burners, so this has become more of an issue. Since looters and burners are treated with kit gloves for political reasons, I foresee this becoming more of an issue in the future. The scum have been emboldened by not being dealt with properly, so I think this issue will grow.

Other than that, I just can't see any other realistic SHTF scenarios.

Any other ideas?