These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Crowning Music of Awesome: Yuki Kajiura certainly knew what she was doing: the Celtic influence on the music parallels its influence on the story. The DVD for .hack//SIGN gives the option to turn off dialogue and leave only the music.
Fan Wank: Early romance fanfiction retconning Tsukasa as a biological male is the most egregious of Fan Wank behavior in the .hack fanfic community.
Considering B.T. frequently has chats with Sora, she was killed by him a few times in the game, and attacked by two player killers in a dungeon. This eventually becomes a joke in .Hack//GIFT, where absolutely no one is surprised to see that B.T. was murdered yet again.
All you have to do is yell out "I'm stuck in the game!" or "I can't log out!" around anyone who has seen this show, especially in an MMORPG, to spark laughter, or joining in.
Viewer Gender Confusion: Macha is a girl. Though due to the lack of any clear feminine characteristics outside of being part pink, it's next to impossible to tell from watching the show alone.