So who's your favorite super mutant in the fallout games? Nightkins count too
My personal favorites are Markus. After all the games he's still alive and has done a lot of good things
The Lieutenant would be my second pick because of his badass death animation
Having only played FO:NV, I'd say Davidson.
He was the first Super Mutant I met that didn't charge at flank speed on me right away and he was... Well, interestingly nut.
I even ended up helping him for what I could. Beside him, only Tabitha sported some interesting personality which wasn't dull such as Marcus (in New Vegas context) or Neil...
Lily, as a companion, has a major weakness: her voice. Very disturbing. Her story was good but couldn't stand her loud ramblings for very long.
Cheers!