Pretty much have the entire 85 Bears team--
I was on a soccer team w/ Jared Payton when I was in 5th grade -- Walter never missed a game -- He signed a whole bunch of stuff, and got me a ball signed by the entire 88 team(5th grade for me)
I helped work the Brian's Run events, which always attracted former and current Bears players, during HS. So I have a lot of the mid-nineties bears too. Jim Flannigan was the nicest guy.
Don't have that many baseball items signed -- But the best is definitely a signed Griffey Rookie card...
at the other end of the spectrum, I have a signed Batting Practice HR ball from none other than Bob Scanlon.