This is what happens when I'm out of touch for so long! I miss the changing of the guard! So here are a two of the lighter John focused fics that I've written over the years:
On Duty - on a rare day off John takes a good look at his boys (pre-series - Dean's 13, Sam's 9) [PG - gen]
The Gift - The Winchesters are given an unexpected "gift" in return for a successful hunt; it makes for an interesting weekend. [PG - gen]