Recently, I've heard of people getting gifts from NPCs that they've become friends with on a regular basis. Personally, I've gotten a gift on all of my characters, but only once in the game. On my first character Lydia gave me Wine. On another, Idolaf Battle-Born gave me Nord Mead. On my most recent one, Jarl Balgruuf gave me a whole lot of Black Briar and Honningbrew Mead.
My question is, what triggers these gifts? And how many gifts have you received?