Let me tell you about my boy, Snake.
Great character. Was always a fan of the Metal Gear series, but seeing how much of a set up character he is in Brawl I was not keen on playing him. However, I tried him out and my goodness he's fun. Grenades are an amazing tool that require a little thought, but once you get it down they're a great offensive and defensive tool. Nikita is insanely powerful. C4 is fun, especially if your opponent isn't mindful of it until it times out. Utilt kills insanely early, dair has so much pressure, and ftilt comes out very fast and has a lot of knock back. I'm not used playing this way so maining Snake has been a bit of a chore, but it's all fun.
Also, honorable mentions: Wolf, Richter, Incineroar, Inkling, and Pokemon Trainer.