As white, I'm a d4 player:
Nimzo-Indian with 4. Qc2
Exchange QGD
Flick-knife attack
Samisch KID
Fianchetto KID
London System
Gruenfeld with 4. Nf3 and 5. Bg5
Benko Gambit Zaitsev variation
Mainline Slav
QGA with 3. e4
As black, I'm a French/Dutch player:
Classical French
Closed Tarrash French
Mainline Advanced French
Leningrad Dutch with 7. c6
Stonewall Dutch with 6. Be7
Staunton Gambit with 4. Nc6
Dutch with 2. Bg5 h6
Reversed closed Sicilian
White: Colle-Zukertort
Black: Benko Gambit, Scandinavian Defense
As White I play 1. c4, the English, and then usually continue with 2. g3 (against 1...e5) or 2. Nf3 (against most other replies).
I play the Caro-Kann against 1. e4
I play the Slav against 1. d4.
I aim for a Caro-Slav structure against 1. c4 (with 1...c6) and 1. Nf3 (with 1...d5).
I've also played other lines (I change repertoires every so often) and sometimes like to surprise my opponents, especially when I have the White pieces.
As white, d4
As black, Caro-Kann, and Queen Gambit declined.
Solid, strategic, no need to learn dozens of lines.
Why would I give away my repertoire?
White: E4. Black: Caro-Kann
White: d4
Black: King's Indian Defense
White: e4 hoping for e5 so I can play kings gambit. I suck at d4 openings.
Black: vs e4 e5 hoping for Schliemann if we start Ruy Lopez, vs d4 Nimzo-Indian hoping to put a knight on e4 supported by Bb7 and f5. Occasionally play French, Winawer if possible. I usually lose with this against good players but the unusual positions u can end up with are really interesting.
c4
...c5
As white:
1. e4
Classical or Panov-Botvinnik against 1... c6
Mainlines against 1... c5
3. Nc3 against 1... e6
Ruy Lopez against 1... e5
(Mainlines with Nc3 against 2... Nf6)
(3. d4 against 2... d6)
Mainlines against 1... d5
As black:
French Defence or 1... e5 against 1. e4
French:
Winawer mainlines against 3. Nc3
Mainlines against 3. Nd2
Mainlines against 3. e5
1... e5:
2... Nc6 against 2. Nf3
Ruy Lopez: 3... a6
Scotch: 4... Nf6
Italian: 3... Bc5
Ponziani: 3... Nf6
3. Nc3: Four Knights mainlines
Modern Defense against 2.f4
2... Nc6 against 2. Nc3
2... Nf6 against 2. Bc4
Really not wide, just detailed.
The Title says it all.