Let's see... my favorite openings would the "Red Fraction" from the anime Black Lagoon, "Hacking to the Gate" from Steins;Gate and "Easy Go" from Katekyo Hitman Reborn!. Concerning the endings, it would be "Beauty of Destiny" from Persona 4 - The Animation, "Homework ga Owaranai" from Yu Yu Hakusho and "Sky-Clad Observer" from Steins;Gate. When it comes to my favorite OSTs, I'd say it's "Prologue" from Katekyo Hitman Reborn! (even though I hate the recaps where this music is used -.-), "Time for True Revelation" from Persona 4 - The Animation (yeah, I know that only the instrumental version of it got its release as of now...) and last but not least "Mifune" from Soul Eater.