What's cheap? Falco/Fox, in my opinion. Despite the ease of use, his rapid kick thing (and all of his smashes) can hit full circle save for below you or under/behind you. Short jump spam, as well as a aerial downsmash that renders you completely useless if you're off the edge, an up-B that does an unnecesarily high amount of damage and distance, and is powerful and fast in just about every aspect.
Personally, there are people like Bombsoldier who actually play as them, but I find the majority of players to just use the C-stick for the entire match until they win.
Secondly, I've always thought Samus's fsmash was cheap, because it's reach surpasses the actual length of her arm, which always throws me off. Not really, cheap, per se, but some pretty lazy modeling.
Thirdly, Marth.
Fourthly, chain-grabbing.
That's about it. Despite my scrubbing, these are easily overlooked problems, and I can usually take on even the cheapest of Marth's and Fox's, but the majorities of the particulars bother me.