The impressive accuracy of deep neural networks (DNNs) has created great demands on practical analytics over video data. Although efficient and accurate, the latest video analytic systems have not supported analytics beyond selection and aggregation queries. In data analytics, Top-K is a very important analytical operation that enables analysts to focus on the most important entities. Everest is the first system that supports efficient and accurate Top-K video analytics. Everest ranks and identifies the most interesting frames/clips from videos with probabilistic guarantees. Furthermore, it supports user-defined functions to rank frames/clips based on different semantics using different deep vision models. Everest leverages techniques from computer vision, uncertain databases, and Top-K query processing to return results quickly.