LIGO’s detections of gravitational waves from binary mergers made history and continue to yield insights into gravity and extreme matter.  With more detections, unusual mergers will yield ever more information.  What other gravitational wave signals will be detected, from LIGO to Cosmic Explorer?  What physics and astrophysics will we learn from them, especially in tandem with other astronomical messengers?  I summarize some highlights of detections of binary mergers in LIGO data and current searches for other signals, and sketch the exciting frontier of what could be learned with future searches ranging from next year to the era of Cosmic Explorer.