Day One

In which there are two agents who have a place among the Avengers as favorites.

There are two best friend agents, Agent Kayla and Agent Jessica, or Jess or Jessie if you don't want to be murdered with a bag of flour. Both are skilled, and have made the tower a generally almost death free zone. Almost.
Kayla is the more serious one, and helps Jess out of trouble a lot. Jess, the really really hilariously notorious fun agent, is Fury's, Stark's, and Banner's favorite agent. Plus Darcy, the Lady of Tasers.

"But you aren't Fury's favorite!" Kayla cried as she ran with Jessie, both holding various snack cakes.
"And you deny this fact every day!" Jess responded back, mouth full of donut holes.