I have the Topeak multi-tool and I definitely recommend it. I like its design. It slides in half and each side adjusts the other, AND it has a chain breaker.

I also carry with me a few spare allen wrenches because I don't like trying to torque my multi-tool that much ... afraid I will break it because my wheels are often on so tight.

Of course, I have spare inner tubes, a patch kit also, a pump, a presta adapter, 2 plastic tire levers, and an adjustable wrench.

I also recommend carrying zip ties with you.