Pikachu is my character of choice, and I make sure not to spam ANY attacks. He's an extremely mobile arial and ground character with probably the best recovery range of any character in any game. Plus, his moves are easy to learn, and his smashes and grabs are mid-range in terms of power and utility. Plus, his moves are nearly identical in all three games, so you can play him no matter what.
The best thing about Pikachu is that if you don't spam his attacks, no-one feels too bad losing to him. Losing to a low-tier character can be an insult to your skill, while losing to a high-tier character makes you feel like they won because the character was broken. Pikachu is just so average (aside from his mobility) that losing to him doesn't make you feel ashamed or cheated.
Plus, he's cute and his final smash is very balanced.