My vote goes to Bill Garnett. He had a lot of help around him but he was simply dominant for 2 straight years when Wyo. went to the NCAA tourney and then gave Georgetown all it could handle. He was to my knowledge the highest drafted Wyo. player ever ( 4th pick). He was a great rebounder and scorer in the paint. No one could play him one on one. Back when the WAC had Utep under Don Haskins, and BYU had Danny Ainge, and SDS had Michael Cage, Garnett still stood out.
My vote for best football player would have to be Randy Welniak. He was the most athletic and clutch QB that I've ever seen at Wyoming. Quick feet and incredibly accurate passer on the run or in the pocket, he engineered many great comebacks under Paul Roach. Wyo. went 16-0 in the conference in two straight magical seasons.
Not a "player" but I have to mention Shauna Smith (from Sheridan) who was NCAA champion in the 400 meter hurdles about 4 years ago. To see her run in person was an incredible treat. She has set conference records that may last for decades.