Locks that work

There is no best rope lock. All rope locks can be cut more or less with garden shears. No security from them at all. Sorry.

I'm taking you mean cable lock, not even the armoured cable locks, so therefore since even the armoured cable locks cannot be left for long, then regular cable locks should be avoided at all costs. If you wish to avoid weight and size, then invest in locking skewers, and at least a lock from the list in the Secondary Locks thread. That would be the bare minimum that I could suggest.

The locking skewer options are in the list on the first page of this thread. Hope that was some help at least.

Some thieves don't even use cable cutters to defeat cable locks, some years ago I saw several cycle racks in town that appeared to had been raided. There were bits of twisted up cable locks hanging from the bars and littering the ground, and several bikes with bent frames. The thief/thieves had obviously twisted up the locks using the bike frames for leverage until the lock or the bike broke. The racks were in clear view on a moderately busy high street too.