Time to sharpen some wooden stakes

from here and here (image source)

If you look closely at the right hand side it does seem to be bent outwards, which suggests the force came from inside the cemetery. It's also fairly low to the ground, which makes me wonder - is this a pet cemetery?

I see a Password111111111111111 in your future

found on Reddit

I suppose at some point you'd need to use different numbers besides just 1, because it'll become difficult to remember how many 1's you need to enter.

Deterrent Win

found on Reddit

Apparently this was the result of a tree rather than a dog, but would-be trespassers don't need to know that.

But not about riding it

from here and here (image source)

I don't see any opening except at the top, so I have to assume this bike isn't going anywhere with thieves OR it owner.

So much for good fences making good neighbours

found on Funny Junk

Privacy is, unfortunately, something that can be pretty easily violated simply by disregarding social norms. In this case, however,  there are all kinds of possible solutions (a taller fence, a paintball, a high powered laser pointer, a well aimed/focused solar cooker, etc.)

Whatever gets the job done

found on Izismile

You know what they say, if it's stupid and it works then it's not stupid. This may not be barbed wire, but that doesn't mean it won't have the same impact, and from the looks of it I think it probably could.

Richard Feynman on Getting Arrested by Los Alamos Fence Security

Watch on YouTube

This is, generally speaking, still how authorities react when you exploit security weaknesses. They want to arrest you, and if you don't have permission to do what you're doing then they may have a point. Richard Feynman did have authorization to be on that base, however, so I'm sure his detainment wasn't too serious. This isn't the only way he trolled security personnel, mind you.

You shall not pass

from here (image source)

You might be like the person who put up this sign and fence and think that the sidewalk there is for people to walk on, but in reality it's only purpose is to keep people off the grass. Take that away and people will be wearing paths in the sod in no time at all. If you don't want people going through the area then you're going to have to fence off more than just the sidewalk.

What a thoughtful deterrent

found on Izismile

I guess "trespassers will be prosecuted" didn't really convey an accurate threat model to the thieves.

You're gonna need a bigger fence

found in Imgur

When people don't care about security, they're bound to do a half-assed job of preventing unwanted outcomes.