Pirates
Pirates are almost the opposite of Ninjas - like that's a surprise to anyone any more. They are loud and boisterous and - okay, they still kill people, but in a more good-natured and jovial way than Ninjas do. They also don't suddenly appear from the shadows like Ninjas do, but suddenly appear they do. With their pirate ships, they sail in on the high tide and pillage a Base before anyone knows what's going on. The Pirates strength is movement, they can move their minions around like nobody else, and moving is very powerful indeed in Smash Up: effects that would trigger when a minion is played on a base are not triggered when a minion moves there. Pirates are completely under the radar. Arr!