Curie, Deacon, X6-88. All of which had fit into my character's story quite well. 
 
I like Curie primarily because of her romance story. I've always found it interesting when something synthetic becomes more sentient and feels emotion. Thought it was a perfect fit for my character. 
 
Deacon, despite his and the Railroad's ultimate fate in the end, made for a good best bud for my character and shared a lot in common. During my character's time in the Railroad, he was a good companion. Made End of the Line all the harder to do for my character.
 
X6-88 is just stone cold and someone you can rely on and trust to the very end once you earn his loyalty. Made for a good replacement after Deacon, and he doesn't lie and make [censored] up so that's always nice not to deal with. 
 
Not too fond of either Nick or Piper. Too goody two-shoes for my taste. Though the same can be said for Curie, she doesn't nag when the Institute take over.