I don't know if this has already been reposted and to be honest I just can't be bothered looking for it if it has.
I'd say there's 4 which affected me the most.
Anna Svidersky: http://www.mydeathspace.com/article/2006/04/25/Anna_Svidersky_(17)_was_stabbed_to_death_in_front_ of_her_co_workers_at_McDonalds
Kyle Anthony Cooke: http://www.mydeathspace.com/article/2006/10/01/Kyle_Anthony_Cooke_(19)_fought_Cancer_for_nearly_6 _years_before_dying
Brad Andress: http://www.mydeathspace.com/article/2006/10/25/Brad_Andress_(20),_from_the_band_Close_To_Home,_di ed_from_Cancer
Adam Riaz: http://www.mydeathspace.com/article/2006/12/13/Adam_Riaz_(17)_died_of_Leukemia_a_month_after_his_ family_perished_in_a_fire