I seriously LOVE singing (I'm not good at it though X-D) so I vote for singing in the line... this will sound maybe childish... but, here's what I think we might do:

-Guess the song. Someone sings a fragment and wins who says first the title of the song. This is cool because if we are not good singers, the game gets more interesting X-D (VAMPS and Hyde's songs in english)

-Daring to sing. Saying a word inside a verse of a song (you must know at least that little bit of the song) then you dare someone to sing a fragment with that word on it, if the song the person sings is not the one your thought of, you can dare someone else. (VAMPS and Hyde's songs in english)

-Senseless Stories. We write VAMPS related tales collectively: We take a piece of paper and say out loud a member of the band (or J) then write a sentence about they doing something, but leaving the last word or 2 words in a line lower, so we can fold the piece and hide the main body of our sentence, then the next person chooses another member and links the new sentence to the visible words, and so on until all members are on it twice, then we read aloud the senseless tale.

-Scenic guess the song. Like guessing the movie, but using VAMPS's and Hyde's songs, in teams. We choose a song and tell the name to a member of the other team, that will somehow act the song for their partners to guess the title.

-Concentration when singing. Two persons choose a different song, but don't say which one, they both start singing loud at the same time, the first that forgets the lyrics or stop (without having finished the song) loses. The rest of us serve as judges. If they choose the same song, they automatically win.

Now, I might sound simple X-D I am very simple and make many silly things, but I have fun with them hehe. Maybe we could record the games and edit some footage for a short clip as a memento from the show, maybe VAMPS would like it, have a laugh, who know?