Baseball. 1)clothing is tzniusdig 2) good exercise 3) not intrinsically dangerous like football or hockey. Kiddush Hashem was made by one of the most famous players, Sandy Koufax, who refused to play on Yom Kippur (I think).
Sandy Koufax did refuse to play on Yom Kippur
Alan “Shlomo” Veingrad was a NFL player who became a chabadnick after his career