The Perfect Grow Room Concealment
You're building a house and you want the perfect grow room. Everyone knows that you need a basement for this. So, you build your basement.
Now, a basement's great, but everyone knows that the basement is the first place the cops are going to look if you get busted. What do you do about that? Simple - you build a trap door in the floor that leads down a staircase to the subbasement. Great, but there's still a problem. Any savvy cop worth his snuff is going to know to look under that Persian rug laying on top of your trap door. He's going to find the subbasement. But you've got a plan. Concealed above the ceiling tiles in the farthest corner of the subbasement, you build a spiraling slide that leads to a third basement.
In the third, final basement, you build nothing. Any cop who has been determined enough to reach this final basement will be satisfied enough with his efforts to exasperatedly declare that there are no plants present in your house.
So...you plant the pot in the attic.
Fire extenguisher grenades
This would be a grenade filled with a fire extenguishing solution. There is a major risk of injury or death from smoke inhalation, structural collapse, or burns that is inherent when you're standing 5 feet from a fire with a conventional extenguisher. This grenade would allow you to leave the room entirely to a position where you only have to aim for the doorway to extenguish the flames in that room. If it's an electrical fire, you no longer have to worry about the current following a water stream back to your hand. Arm your brigade with extengishing grenades and have them lob away through the front door or a collapsed roof.