As white, my favorite opening is the Ruy Lopez. Theory is actually somewhat minimal compared to what people make it out to be. The plans are straightforward and give white a comfortable position most of the time, and if black doesn’t know what he’s doing (which will happen most of the time), white gets a really good position. For example:
In this position, white is well-developed, has dominant central space in an open position, while black is cramped and struggles to find much counterplay.
My favorite opening as black is the Sicilian Najdorf. The Sicilian gravitates towards me because I always play for a win- and the Sicilian is arguably the best response to e4 to play for a win. The Najdorf gets a solid position while making use of dynamic advantages, adding a bit of spark to a solid game. I also just hate playing e5.
Against d4, I play the Nimzo-Indian. It’s simple, solid, and active.
I also start with the Horwitz move order (e6) so white can’t play any Trompowsky crap and to possibly transpose into the French.
My Favoriten is for Sure the Sicilian against e4 and KID against d4