Theo de Raadt started OpenBSD in 1995 and still coordinates the project. He is the final word on how the system works, what is included in the system and who gets direct access to the repository. He resolves all disputes that contributors and committers cannot resolve amongst themselves. Theo takes whatever actions are necessary to keep the OpenBSD Project running smoothly.
Many people have very specific coordination roles within OpenBSD — quite a few architectures have a "point man" for issues that affect that hardware, the compiler has a maintainer, and so on. These are people who have earned that position of trust within the community. The only time that Theo acts as the final word is when someone has broken one of OpenBSD's few rules, such as bringing bad licenses into the source tree or behaving poorly with other committers.
This style of organization, with a central benevolent dictator, avoids a lot of the problems other large open-source projects have with management boards, core teams, or other structures. When someone decides to work on OpenBSD, they can either accept Theo's decisions as final or risk conflicting with the main OpenBSD Project. Thanks to the cooperative nature of OpenBSD development, Theo doesn't have to use that Big Stick nearly as often as one might think.