On the way to his fourth title in San Jose, California, on February 1, 1969, Guenther rolled the PBA’s second-ever televised 300 game (the first having been accomplished by Jack Biondolillo in 1967).
The feat occurred during the second of Guenther's four matches broadcast live that day.
Guenther defeated future PBA Hall of Famer Don Johnson in that match, 300–189, then went on to defeat two other future Hall of Famers (Billy Hardwick and Wayne Zahn) for the title.
His 11th and final title was earned just shy of his 40th birthday, on January 3, 1976 at the Ford Open in Arcadia, California.
While Guenther was feared on the lanes, he was well-liked off of them, winning the PBA’s Steve Nagy Sportsmanship Award three times.