AFI #005 Humphrey Bogart as Rick Blaine from Casablanca (1942)

Ilsa: I can't fight it anymore. I ran away from you once. I can't do it again. Oh, I don't know what's right any longer. You have to think for both of us. For all of us.

Rick: All right, I will. Here's looking at you, kid.
Ilsa: [smiles] I wish I didn't love you so much.

- Humphrey Bogart as Rick Blaine from Casablanca (1942)

The bolded line is ranked #5 in the American Film Institute's list of the top 100 movie quotations in American cinema.

In Japan and Korea, the line "Here's looking at you" is translated as "Cheers to your eyes".

This phrase is actually a toast that originated around the fights that occurred in the pubs of old. It was commonplace for a patron to wait until his adversary was drinking from their stein of ale (and their vision was therefore blocked by the stein) to attack ... it bettered their odds of success. It is led to the development of the glass-bottomed stein in which the drinker could keep the other patrons in their vision even when drinking.

Thus came the toast "Here's looking at you"