For the ultimate in home security, you need a fortified offshore tower armed with muzzle-loading cannons.
This gun tower in Pembroke Dock, Wales, UK, was built in 1851 to protect the harbor from invasion. It was manned during World War I and II, when the UK was again under threat.
And now it's for sale! You can buy the fort and live in at as a home for a mere £70,000 ($87,000 USD). Here's the real estate listing.
It even comes with the original cannons! Really, the place has everything you could ask for in a residence. The Daily Mail reports:
The Grade II listed tower has substantial curved walls that are 13 metres high and up to 2.7 metres thick in some parts. [...]
It is accessed via a long walkway built on land owned by the Crown Estate, which would be leased for an annual 'peppercorn' rent, according to John Francis, the estate agent handling the sale.
A peppercorn rent is a nominal rent--usually consisting of a single peppercorn. I suggest trying to buy the walkway, then rigging it with demolition charges for emergency use.
-via Ace of Spades HQ