My favourite one is World of Warcraft, besides all the hate and problems it has, I've been playing for a lot of years and I'm still enjoying it. I've met a lot of people there that now are great friends in real life even many of them are not playing…
World of Warcraft, the Burning Crusade expansion Box is my favorite till now. Dont know if is because of the nostalgy of those times, the lore behind it or because the art in it but is for sure my favorite one
My favorite experience with Warhammer 40K tabletop was playing with my friends on my fathers garage. We wer playing for days in summer including all night long... great times