From ESPN game notes:

Aaron Rowand had a walk-off single Friday in the Giants home opener. Aaron Rowand had the walk-off hit in the Giants home opener last season too - against the Braves in the bottom of the 13th inning. Friday's hit was in the bottom of the 12th inning. It is the 6th career walk-off hit for Rowand. According to the Elias Sports Bureau: the last player to have a walk-off hit in back-to-back home openers was Toby Harrah of the Texas Rangers in 1976 and 1977. Harrah hit a walk-off single in the 11th inning in the 1976 home opener and a walk-off HR in the 10th of the 1977 home opener.