This list was suggested by Mark Wallace, and I am taking some of these on trust as they are from films I haven't seen and, in the case of Evil Dead 2, have no desire to see.
Marlon Brando as Stanley Kowalski, in A Streetcar Named Desire. From Omer Lev and Jess Bowie.
Bruce Campbell as Ash Williams, after he straps a chainsaw to his stump, Evil Dead 2. Nominated by Twlldunyrpobsais.
A minion's response to Silas Ramsbottom introducing himself, Despicable Me 2. From Tony Payne.
4. 'Ahhhhhhh… ahh… ah… ah…ahhhhhhhhh'
Tarzan. Thanks to David Lindsell.
Career advice to the Graduate. From Western Independent and Omer Lev.
Orson Welles as Citizen Kane. Possibly the most famous, although I've never seen the point. Nominated by many, including, er, Citizen Sane.
Al Pacino as Sonny Wortzik, Dog Day Afternoon. Nominated by Omer Lev and Robert Epstein.
Severus Snape, Harry Potter and the Deathly Hallows. From Lutra Nippon.
9. 'Supercali- fragilistic- expialidocious'
Mary Poppins. Nominated by Labour History Group.
Major Clipton, The Bridge on the River Kwai. Recalled by Richard T Kelly.