I have a soft spot for tge Grey Death. Decision at Thunder Rift was my first Btech novel the year it published. That book has shaped how i see mercs in Btech ever since.
More recently, I really like the Chao Irregulars stories. As silly as Mech gymnastics was, I think the stories were well written and the unit is easy to like.
But my favorite by far are The White Hawkes; a scrappy merc company perpetually on the verge of financial ruin set in 3026. Lead by disgraced FWLM Captain, Deacon Hawke. 😁
I've played them, or versions of them, for decades now. 😊