Joe Dimaggio's 56 game hitting streak. Pete Rose came fairly close with 44, but the pressure was tremendous. And you can add Ted Williams hitting .406 in 1941, also.
Personally, I feel records set in 1941 are a little tainted, as several major leaguers were drafted during the 1941 season. Selective Training and Service Act, or draft, was signed by President Roosevelt on September 16, 1940. Most notable was Detroit Slugger Hank Greenberg, a celebrated star of the time and future Hall of Famer, received his draft call on May 7, 1941.
Conversely, Ted Williams was not happy being called up for active duty in the Korean War, which cost him an additional two seasons, adversely affecting his career stats. BTW, Williams was John Glenn's wingman in the Korean War.
Similarly, records set in 1961 American League (e.g. Maris 61 homers) were enhanced due to expansion from eight to ten teams.