My favorite was Mouth (Corey Feldman). I laugh my head off everytime I watch the Spanish translation scene.
Data. . . .no question about it.
Not to mention some of his quotes. . . . "They can't wait until tomorrow when they foreclose on all the what-ever-you-call-it". . . .
Data's inventions were quirky and creative. I also get all choked-up inside when his dad tells him "you are my greatest invention" at the end.
Mouth was a strong character and probably my second favorite.
I just bought that dvd the other day; it was in a two-pack with Beetlejuice.