On Jeff Conine's web page there is mention of his 1995 All-Star Game home run off Steve Ontiveros. The reference is correct, but the link is to the "other" Steve Ontiveros who played 3rd base for the Giants and Cubs in the 1970's rather than the Oakland A's pitcher who gave up the homer.
Original text:
"...That season, he was named All-Star MVP after hitting the game-winning home run off Steve Ontiveros to lead off the eighth inning."