These are the things I included into my customized knoppix, so perhaps if it can be considered for inclusion in the original knoppix :-

1. Cairo-dock inside compiz/lxde
2. Browser plugins :-
a) Java for running applets.
b) gecko-mpalyer plugin to play DivX, Quicktime, RealVideo, Window Media player files.
( Also mean included mplayer, gnome-mplayer and various codecs ).
c) Adobe Flash ( already included in knoppix ).
e) Adobe Reader ( already included in knoppix ).
3. Browser extension :-
Download Helper
4. Bittorrent and emule software.
5. K3b
6. Sun Virtual box
7. Pidgin Messanger