Since @MatthewHecht already pointed out that Hawkman’s first panel is not on here, since the first appearance of both Jonah Hex and Shazam! are not on here and since @Shayera.Hol took care of Hawkgirl I’ll go with two other favorites:
I see someone already got Cass and Talia! I’ll get proper images here later, because I don’t have the images on hand and actually can’t remember the first words Jess spoke on-panel, but while Knox got pre-Crisis Jason, it’s worth noting that to my recollection, the first word Jason speaks on panel post-Crisis is “oops” and it’s honestly pretty on-brand.
If we’re talking about his post-Crisis origin story in Batman #408 (and not the handful of preceding issues that fall into the post-Crisis-but-maybe-still-Earth-One haze), then you’re pretty much right.
And here’s that picture of him smoking again. You gotta have that.
I’m just going to post the first words of every DC character I’ve seen the first appearance of:
1938
Kal-L: “Make yourself comfortable! I haven’t got time to attend to it!”
1939
Bruce Wayne: “Well, commissioner, anything exciting happening these days?”
Jim Gordon: “-No-o- Except this fellow they call the “Bat-Man” puzzles me!”
1940
Thomas Wayne: “W·What is this?”
Martha Wayne: “Thomas! You’ve killed him. Help! Police… Help!”
The Joker: “Tonight, at precisely twelve o’clock midnight, I will kill Henry Claridge and steal the Claridge Diamond! Do not try to stop me! The Joker has spoken!”
2019
Wink: “Hi. Seriously? Three submarines, one carrying a nuclear warhead, and they’re the “crown jewels of your nation”?”
The Aerie: “General. I don’t want your soldiers to die. But they will unless you act. Evacuate your subs.”