RGIII seems like a no brainer. He may have the one of the most popular brands in the NFL right now. He was the most marketable rookie in NFL history, having signed endorsement deals with Castrol Motor Oil, EA Sports, Subway, Gatorade, EvoShield, and adidas before his pro career even started.
There's no questioning RGIII's talent and marketability, but the risky part of investing in him would be his chance at sustaining a long career. He's already had two surgeries for a torn ACL, and while he has shown he has the determination to overcome it, the threat of a major injury looms simply because of his playing style. Simply put, he's a few big hits away from seriously jeopardizing his career, which would wipe out any chance he has at having a long, lucrative career.