Someone mentioned Elizabeth companion. I haven't tried her yet, but I will once I start my next playthrough when The Frontier is released.

Willow and Niner are my favourite modded companions. Niner is pretty funny, but I only used him once. Willow is the only companion who I have on my modlist all the time, Willow also comes with a dog so that's a plus. I don't really care about vanilla characters.

Fallout 3: Fawkes, cause damn, that dude was both intelligent and a badass mofo.

New Vegas: Boone, also another badass, but with a tragic backstory.

Fallout 4: Cait, especially after you do her personal quest.

Vanilla: Boone,his history made me like him more,and his hate for the Legion too.

Modded: Russell,Badass Desert Ranger who hates the legion and has a dramatic story worthy of a movie.