If You Had To Choose 7:

[scribbleMind]

Secret Six
Shazam
Animal Man
Dial H for Hero
Doom Patrol
R.E.B.E.L.S
Green Arrow

But this is primarily based on the people around me personally. I know I will never convince them to read a Superman story, and I also know that they are interested enough in Batman that if I were to get them into DC comics in general they would find their way to Batman eventually. My people lean towards quality stories that feel both niche and complete.

[Green Goblin of Sector 2814]

Seven series:

1. Wolfman/Perez New Teen Titans
2. Levitz/Giffen Legion of Superheroes
3. Geoff Johns Green Lantern
4. Giffen/DeMatteis Justice League
5. Mark Waid's Flash
6. Chuck Dixon's work with the Batman and Bat-family books
7. Rucka/Brubaker's Gotham City Central

Honorable Mentions: the Knightfall and Death of Superman sagas

[Lee Stone]

It would depend on the person, really.

I would first find out what their favorite shows and movies are and try to match them up.

Unfortunately, almost all of DC's books would fall under one genre, even one type of that genre, so I probably wouldn't recommend any unless they listed Flash or Arrow.
And then, I would send them towards:

1. Batman: Year One
2. Green Arrow: The Longbow Hunters and the series by Grell
3. Catwoman: Her Sister's Keeper
4. Wonder Woman by Perez
5. Sandman Mystery Theatre
6. The Question by O'Neil
7. The Suicide Squad by Ostrander

If they list the MCU films, but not Flash or Arrow, I'd stick to Marvel.
If they don't list the MCU, Flash or Arrow, I'd steer them more towards Dark Horse, Image or Dynamite.

[Ulysses]

I'd want to point them towards stuff that leans self contained.

Batman Year One or Long Halloween.
Catwoman: When in Rome.
Green Lantern: Willworld.
The Question (O'Neil).
Kingdom Come.
Wonder Woman (Azz).
Aquaman (Veitch).

[TheRay]

I'd go with the more obscure as they would likely find their way to the bigger names eventually:

#1. S.T.R.I.P.E.
#2. Isis
#3. Lightning Lass
#4. General Glory
#5. Goldstar
#6. Mr. Miracle
#7. Spy Smasher

[Air Wave]

Well, just did a count. I tried to consolidate your answers into characters or brands/franchises.

Unsurprisingly, these are your top 7:

SUPERMAN
BATMAN
WONDER WOMAN
The FLASH
GREEN LANTERN
JUSTICE LEAGUE
TEEN TITANS

[Jim Kelly]

If I'm going to indoctrinate someone into the DC culture, I want them to see stuff that they wouldn't normally be exposed to--concepts and genres that show the whole breadth of what DC can offer. The last thing I'd want is to give them the impression that DC is just the obvious seven super-heroes--Batman, Superman, Wonder Woman, Flash, Green Lantern, Aquaman, Supergirl.

[Air Wave]

I think for me this is about generally introducing someone to comics in general (which for me would naturally begin with DC). Probably a child. So I would try to find a broad range of the biggies and let them go from there. So in that regard the above list makes total sense.

[jsafanforever]

I'd try to show them the titles that I had growing up that pulled me into reading DC almost exclusively.

1. The New Teen Titans (1980) by Wolfman and Perez
2. Suicide Squad (1986) by John Ostrander
3. Crisis on Infinite Earths (1985) by Wolfman and Perez
4. Watchmen (1986) by Alan Moore and Dave Gibbons
5. Batman: The Dark Knight Returns (1986) by Frank Miller
6. Legion of Super-Heroes "The Great Darkness Saga" (1982) by Paul Levitz and Keith Giffen
7. All-Star Squadron (1981) by Roy Thomas and Jerry Ordway