combo locks
Anything with a combination is instantly vulnerable to means that involve no physical harm. $10 four-dial combo cable locks can usually be opened in under 30 seconds by someone that has half a clue what they are doing. These are not secure at all. Even better combination locks are 100% vulerable if a thief has enough time and patience to methodically work through the possible combinations. If you must use a combo lock of some variety, choose one that is least likely to be vulnerable to brute force (trying all the combinations) and manipulation (feeling beside number wheels with a thin piece of metal for grooves) attacks. Combo locks seem like a pretty bad idea to me in general.
The combo locks with 4 dials normally have 10,000 possible combinations, so if you can try one combo and move on to the next in 1 second, you're talking 1 hour and 20 minutes to try half of the possible combinations.
But a person who's good with combo locks can probably figure out the combination in a minute or two.