For Jagged Alliance 1: Tex. He's hilarious. Super happy he's back. I'm assuming he's actually going to be good, like he was in Unfinished Business.
For Jagged Alliance 2: Trevor. I love his vibe, and while he may be expensive for his level, his skills make up for it and progress super fast thanks to his high wisdom. Malice and Meltdown are fun ones for early game. The first time Malice saw a Crepitus, I was laughing so hard I could hardly breathe.