I think Sudan, Egypt, and Libya would be contenders. I suppose there's probably a general principle at work that if your country's borders were decided not by geographical or cultural boundaries but rather by an occupying bureaucracy, then there's a high probability of squareness.
Or if your territory is made up partially of land the ownership of which isn't a pressing concern for anyone because it doesn't support a population and has few resources.
The western part of the boundary between U.S. and Canada is unusually straight, but I suppose that was an expedient agreement at a time when neither side wanted to go to war over it. Not that relations were totally peaceful or friendly.
And back on topic, Switzerland's Wanderweg paths are numerous, very well signposted with bright yellow signs, and excellently maintained as well as clearly described in numerous guidebooks. Walking the countryside in Switzerland is a joy.
And Switzerland features the most drop-dead-gorgeous hiking maps of any land I've visited. It feels like each mountain was hand-drawn and shaded by someone who knows and loves it, and you can often ID them from the ground based on the pictures. But the artistic details are still subtle enough not to interfere with the roads, trails, POIs, and text.
Or if your territory is made up partially of land the ownership of which isn't a pressing concern for anyone because it doesn't support a population and has few resources.
The western part of the boundary between U.S. and Canada is unusually straight, but I suppose that was an expedient agreement at a time when neither side wanted to go to war over it. Not that relations were totally peaceful or friendly.