Scattered around our part of Texas are these lethal looking Honey Locust trees. From a distance they look pretty but when you get up close you start to see these 3"-4" thorns all over the branches. The thorns are not soft either, they are very hard and can actually be nailed into softer woods.
Note the secondary set of smaller thorns on each of the main thorns. Ouchie.
There are a couple in the park down the street from us:
Sorry about the soft focus in the last shot. You can see that it is just short of 3". The longer thorns were higher up the tree.
Who needs barbed wire when you could just plant these around the perimeter!