I generally choose 2 from: Rabbid Peach, Rabbid Luigi, Luigi.
Rabbid Peach and Rabbid Luigi both provide healing capabilities, and both have multiple dash attacks. Luigi has neither, but has mobility and range, so he can be good for some missions. Luigi does also have overwatch.
I’ve used some others situationally, but I don’t care for the shotgun mechanics (pure personal preference), or some of the AoE damage effects (i.e. Rabbid Mario’s dashes), because I don’t like the potential for friendly fire damage.