For some reason the modestly cheapo combination lock on my wife’s bike jammed the other day, whilst it was locked up outside school.
Hopped out to the hardware store and bought some small bolt cutters. One quick snip later and we were done. I think that there are only two kinds of locks worth having,
1) Super small, light lock that you can carry anywhere ‘just in case’. Won’t stop a bike thief, but will stop a casual scally from riding your bike away while you take a crap or whatever.
2) Big F-off lock for securing your commuter/transport bike.
Anything else in between is pretty much a waste of time.