Concertina wire works way better for keeping people off your lawn... they try to get through and it just snags and tears and makes life difficult...
Actually, if you want an effective barrier that doesn't have people thinking you're some sort of nut, do it with plants.
Make a bramble rose hedge. That is, use blackberries or raspberries alternating with rose hedges. The rose hedges tend to fill down and out, while the bramble canes arch over. Gorgeous, useful, moderate maintenance required, and it's as effective as the concertina.