Statistically for me, as an e4 player as white and a c5/Nf6 player as black, I face the sicilian the most with both colours. Feel free to check out your stats either on the chess.com explorer feature or using tools like openingtree
What is your most used opening in chess?

As white I play 1 d4 2 Nf3 3 g3 4 Bg2 5 0-0 6 c4 in that order, but it does depend on black's moves.
As black I play the Tarrasch Defense against the Queen's Gambit and play Tarrasch Defense type setup against white's queenside openings.
Against 1 e4 it's the Petroff.
In my overall repertoire when white or black I think the white move sequence is my most used, but it depends on how often black derails it, I've never looked into how often that happens.
That is my set in stone black and white repertoire, I don't change anymore.

The sicilian in various aspects.
I play it every game vs. e4 as black... I play it by transposition from the Van Geet as white... Against the English defense I play the reversed sicilian (1... e5). Against the Reti I play the sicilian invitation.
It's just a legendary defense... even though it's the most common response to e4 this doesn't matter much, it's so rich and gives both sides so many options.
What opening do you use the most?