Even though Spoiler/Ace/Rip/Kroe have special places in my hearts, I'd actually say Shrike. He's just too wacky to not love, esp. since the ES entry you and Izu did. Shrike's character is just great, and his facial expressions are such a contrast to all of his opponents.
It's hard to say which one I like best because all of your characters have great designs, interesting stories and unique personalities! I like Dr. Kroe simply because he's one of those sneaky clever mad scientist villains you just love to hate, MB6 & MB7 are just fun to watch interact, and little robots with top hats are just <3. I want to hug Beebs because he's just one of those big lugs out for a good time (and a few pizzas!). Shrike and Baby are just psycho, and who doesn't love psychos. Spoiler / Dark Ace is probably the one I've had the most exposure to and just has a ton of things I like. Great story, awesome character design, great interaction with other characters (especially Rip) and very vivid personalities. It also doesn't help that I'm a terrible fangirl of bad-asses and cyborgs. ^w^