"1.000 Batting Average"
I sent a request to John Paciorek asking him to tell the story on a baseball about his one game career and this is what I got:
"In the last game of [the] 1963 season I batted 5 time[s]:
walked twice, hit 3 singles; had 3 RBIs; scored 4 times"
"I had a back operation in 1964. I never played in Majors again."
"I have been a teacher for more than 40 years. I have written 2 books "
"and many essays. I have fond memories of playing with Joe Morgan, Jim Wynn, Rusty Staub + Walt Williams"
John played in one game and had a great game! You can see the boxscore here and more info about him here.