Tough question because we have SOOOOOO many from which to choose!! However, Jeff Hornacek is the best basketball player from ISU: Unselfish - could hit the big shot when needed; was calm under pressure; had an incredible basketball IQ - allowed him to be a COACH on the floor; and had a fiery personality that commanded respect & made him DESPISE losing!! (no way that J.H. misses that gimme layup in 2001 Boise disaster - Tinsley was awesome, but I sometimes felt he lacked that extra "fire".)
I look at a wasted piece of talent that was Elmer Robinson (whom J.O. said was the best "athlete" he'd ever coached) - yet, during his Frosh. season he was a difference maker (eg. scored the clinching basket against Mich in '86). Why did Elmer have a good rookie season -- Jeff Hornacek wouldn't let him be lazy on the floor. After Hornacek left, Elmer had no on-the-court leader to get his big & sorry behind in gear on a consistent basis.
Hornacek then spent a "lifetime" in the NBA. In the 1991-92 season he made the NBA all-star roster (scored 11-12 points in that game, I believe). He led Phoenix and Utah into the playoffs, Utah into the finals, and even had an NBA record of 8 straight 3-pointers in a row (has since been broken).
I love all my 'Clones (from The Roland Rocket to Marc Urquart to Ross Marsden), but J.H. was THE key on-the-court general who helped Cyclone Basketball and Hilton Magic become what it is today. That's why he is MY CHOICE!