This list hit my reader earlier this a.m. and I think it's probably the definitive list.
Number 10 - Rocky Marciano's 49-0
Number 9 - Michael Schumacher's 7 championships
Number 8 - Ty Cobb's .366 career batting average
Number 7 - Nolan Ryan's 7 no-hitters
Number 6 - Wayne Gretzky's 215-point season
Number 5 - Wilt Chamberlain's 100-point night
Number 4 - John Wooden's 88 straight wins
Number 3 - Cy Young's 511 wins
Number 2 - Jerry Rice's 22,895 receiving yards
Number 1 - Cal Ripken's 2,632 consecutive games
I'm not a racing fan, so I couldn't pontificate on Schumacher's record, but it does sound like it's the "weakest" of the ten. If I had to pick another that could possibly be broken, then perhaps Nolan Ryan's no hitter total might be. Jerry Rice's receiving total would be next in line, but I wouldn't bet on any of those three ever being broken. The rest will probably stand for all-time.
I did a little research and found other, similar lists and some lists that took the total even higher: