Few ones I remember:
I think it was like 2012/13, and like many said most his pressers were useless, but someone asked him a question about how long they waiting until the snapped the ball, and Bill said something like "oh yeah, we average like 34.6 seconds between snaps" and you knew he knew that number 100%
Another presser like from 2014 when someone talked about that SB Nation article about how K-State actually has the most spread offense out there (in terms of solo tackles, and other metrics) and he got genuinely interested cause he had never heard of that.
On a personal level, I remember at several catbackers events as a kid, he always would make time to talk to all the kids (including me) about how we where doing in school, etc.
And of course, all his little quirks, windbreakers even when it's 90 out, Nike Cortezes, "youngsters", "by and large", making the opposing team, regardless of how good or bad they are out to be world beaters, handwritten slanted notes, pregame music selection.
And I remember as a student after he came back in 2009, always driving by the stadium after a late night, and seeing one car in the parking lot, his of course.
Games I loved were the 2000 snow game vs Nubbs, 2003 winning the Big 12 vs OU, basically the entire 2011 season, 2012 vs Miami (including that loller play behind the back), 2012 vs WVU and Texas, and OU. 2014 vs OU. Actually winning the last few bowl games.
What a ride, but it had to end.