I think Medicham is my personal favorite, as it's a nice mix of two types that can be seen as respective counterparts (Fighting and Psychic), and with Pure Power it hits super hard. It's especially nice that they gave it Zen Headbutt by Heart Scale in Gen VI, thing did me very well in my X Wedlocke and lived to the end. It's one that has plenty to use even if its stats aren't the best out there.
Here are some of the others I feel are worth naming:
Toxicroak - An interesting type combination for this one, and a poisonous dart-frog is something cool to make a Pokémon out of. Despite its nasty 4x weakness to Psychic, it actually has a very unusual set of resistances and good usability.
Scrafty - This one used to be my favorite, I do still like its design and typing even if the Fairy-types knock it into next week. But three very helpful abilities and tons of moves it can utilize make it pretty fun, even despite that glaring weakness.
Chesnaught - This one I may just like for being under-appreciated, or have something to do with the fact that I really like Chespin. I do like the design here, and nice physical stats to throw on it.
I also voted Emboar, just because I kinda feel sorry for the thing and all the hate it gets, and I do kinda like the thing. There are others I could probably mention but these are just the most general choices for me.