hardwood external doors with Chubb deadlocks on them (two each on the back doors)
special lock on the front door
Tall garden gate with Chubb deadlock
sturdy shed with another hardwood door on it (ex-front door)
metal locks on windows with removable keys
laminated glass in patio door
Substantial fire doors fitted with mortice locks
Rated intruder alarm with monitoring
Mostly because I'm rather eccentric, though in one of my early jobs part of my duties included checking security measures at branches of a bank-like institution, and finding that managers often leave the key in the safe door with their bunch of keys hanging off it, because the bunch of keys is so heavy and awkward. Hence all my downstairs locks except the front door are suited to a single key. When I go out I only carry a front door key, a car key, and a key to the keysafe.
Also because used to be away from home for predictable periods, and at that time my neighbour used to have an open gateway in the back wall leading to a wooded area, and their house attracted numbers of young single men of unknown provenance.
my risk profile is now much lower.