Both Agile and Waterfall work for very small enterprises. Agilists will tell you that Agile works better in that environment as the planning process and the project management overhead is reduced to a minimum. However, you must keep in mind that Agile works only for software projects (I wish someone can prove me wrong on this one) and that Agile consists of many "rituals" that may or may not be necessary (such as "daily standups"), and it replaces the PM overhead with other overhead thrown on the shoulders of the team members.
Waterfall, on the other hand, has its downside as it is may create a lot of overhead upfront (which can be overkill for small enterprises). However, once the planning process is done, and the project work starts, then managing the project will be a breeze (you just have to follow the process). Waterfall also works for all types of projects, including software projects. Oh, and the success rate of Waterfall projects is more or less the same of that of Agile projects.