This Reddit thread popped up a few days ago. A friend of a Redditor rented a car in Fort Lauderdale and was surprised to find this just chillin' in the trunk:

My immediate thought would be UHHHH MR. LAMBERT, but the Reddit friends immediately got to work trying to explain why an AR-15 had been left in the back of a rented Nissan.

MEANWHILE...

When Lauren Tannehill, the wife of Miami Dolphins quarterback Ryan Tannehill, returned a rental car this month in South Florida, she accidentally left a big surprise in the back seat: an AR-15 rifle, a Broward sheriff's report says. The rifle, valued at $2,000 and still in its case, remained in the Nissan Rogue when it was rented to another person hours later Jan. 4, the report said.

The Tannehills view this as a "personal matter," according to a Dolphins spokesman Wednesday. The gun is legally owned by Ryan Tannehill, and the couple immediately called the rental car company to report a missing item and was given "the run around," but the couple didn't specify what was lost in the bag, a source said.

"Okay, I think I'm all set with this rental car. Do I have everything? I feel like I forgot something. Let's see. Phone, check. Bag, check. House key, check. Chargers? I always forget my chargers. Check and check. Toothbrush is here. Wallet is here. Got the gift for Nana. Got the rest of my sandwich ... I just can't shake this feeling that I've forgotten something ...

[hours later]

"OH RIGHT, MY BIG-ASS MURDER STICK. DAMMIT."

No one's in trouble or anything. It's a legally owned gun and its misplacement was handled appropriately. Just a very weird thing that happened.