That's a great question, and a common headache for city dwellers! The "best" lock really depends on your main adversary: is it clever raccoons, curious people, or the wind? For most urban settings, you need a lock that's simple, robust, and weather-resistant.
For outright security against human tampering, a heavy-duty stainless steel padlock with a shrouded shackle is top-tier. Pair it with a bin that has integrated lockable hasps. It's the strongest deterrent but requires you to carry a key.
If convenience is key (pun intended), a built-in combination lock is fantastic. Look for bins with a dial combination latch directly on the lid. No keys to lose, and you can give the code to sanitation workers if needed. Just ensure the mechanism is covered to prevent ice and grime buildup.
Now, for the famous urban raccoon—a standard lock might not suffice. They are clever paws! Your best bet is a bin with a locking lid that requires opposable thumbs to open, like a locking bar or a dual-compression latch. These mechanisms secure the lid tightly all around, making it impossible for a paw to pry it open. Sometimes, a simple heavy-duty bungee cord hooked under the bin's handles and stretched tightly over the lid can be a surprisingly effective and quick raccoon deterrent.
In summary: choose a stainless steel padlock for maximum security, a built-in combination lock for daily convenience, and a raccoon-specific compression latch for wildlife woes. The goal is to make accessing your bin more trouble than it's worth for any unauthorized visitor.