Everyone is charmed by TARS including me.
But I have a big soft spot for CASE. He has some of the best lines.
"Maximum velocity achieved. Prepare to fire escape thrusters."
"Learned from the master."
"Cooper, we're slipping towards Gargantua. Shall I use main engines?"
(My personal favorite.)
"Cooper, this is no time for caution."
And the interrupted
"Cooper, there's no point in using our fuel to chase--"
There's something very movingly practical about him.
If it weren't for CASE they never could have matched the Endurance's spin or carried out that slingshot. Brand would be dead and Mann would have taken control of the Endurance.