I was going to suggest elephants as a contender behind certain primates.Heronblade said:Any and all creatures may have that capability. Some just have fewer evolutionary hurdles to jump through.
In any event, apes and other primates are the obvious choice. Raccoons are also in an excellent position.
Elephants and crows are in the second group I would consider. Both have high logic skills, but while they can use tools, said use is extremely crude.
Pigs, killer whales, and dolphins have a high enough level of intelligence to be serious contenders, but as mentioned lack the physical means required to make the most of it. Many canids (dogs, wolves, foxes, coyotes, etc.) and felidae (cats, both great and small) are in a similar position, but are not quite as strong in the reasoning department
I'm not even sure you could regard their tool usage as crude - the trunk, while not as flexible as two sets of opposable digits, is more that adequate for a great number of tasks.
And they're fearsomely intelligent and social - it seems like every few months there's a new study or report saying that they're capable of something previously unsuspected.