Sarah's Mech, a Jenner sold during August 2013 for ten dollars in Mechwarrior Online. Sarah, a young girl who passed away of cancer, got into Battletech via her longtime-fan father and the Jenner was her favorite mech; the developers donated the proceeds to cancer research. At the time of this edit, the sale had netted the charity in question almost one hundred thousand dollars, and still counting.
Jen McQuarrie in 4. As everyone else is going to pieces over the death of Ian's uncle and you have to buck them up, Jen is the only one who realizes "oh man, this was Ian's uncle" and the only one who asks you how you're holding up, rather than needing her hand held.
Damon Squire, also in 4. Formerly Joanna's bodyguard, when the player must choose between rescuing Joanna and raiding the enemy weapons cache, Squire will always go for the rescue, regardless of the player's choice - meaning if the player chooses the rescue mission but opts to "bench" him for it, Squire will tag along anyway as an additional friendly 'Mech.