Gagne-Sakic-Iginla
Nash-Thornton-Bertuzzi
Richards-Lecavalier-Heatley
Smyth-Draper-Doan
St. Louis
Blake-Pronger
Redden-Niedermayer
Jovo-Foote/Regehr
Other than the checking line, any of the top 3 lines could be the "#1". The first line has great chemistry from past world tournaments. Thornton and Nash have chemistry from Davos and the past World Championships, and with Bertuzzi, there is no defense out there who can stop all three from powering to the net. Heatley and the Lightning duo will be a highly skilled line with good skaters. The checking line is three hard working, two way players who won't get pushed around.
St. Louis is the odd man out, and like Draper and Bertuzzi up until recently, his play has been subpar this year, but unlike Draper (defensive specialist) and Bertuzzi (power forward for high-power line and picked up his game), St. Louis does not have any specific role. He'll basically be like Perry before the Colliton injury in the WJCs (13th forward because he isn't a bottom 2 line player).
Blake/Pronger will pound any opposing forward with their head down, Redden/Niedermayer will play a solid two way game, while with Jovo/Foote or Regehr, Jovo can do his thing with the other guy covering his butt.