(I'm not sure if bumping an almost three month old thread is bad, so if it is, apologies)
Looking around the internet, searching for an old piece of artwork of a Mega Clefable. I found it and a few other things, so I figured I would share my thoughts on how they could work. Let me know what you think.
Personally, I don't think Clefable even needs a Mega Evolution, but if it looked like this, I would gladly welcome her with open arms, as this design has a neck and head, which in my opinion I feel is a design flaw with Clefable. Never really liked the Head-to-Neck designs. Anyways through mega evolution, Clefable remains a Fairy-Type, and gains Pixilate, which means she can now gain access to STAB Hyper Voice. Her lighter features tell me she would be much, much faster, but have a light boost to both Attack and Sp.Attack. Unnecessary attack boost is actually a tiny nerf against Mega Clefable for anyone who uses Foul Play against Mega Clefable would deal more damage then before. I imagine this Mega Clefable could become one of the best special sweepers in the game.
I like the idea of the lava veins he's got going on, and it gave me the idea of Golem being a Rock/Fire type. We're talking a Pokemon who already has a four times weakness to Water now losing his original Earthquake STAB. In an exchange, he gains Rock Head, and through leveling can obtain Head Smash and Flare Blitz. This opens up a whole new ballpark as Golen becomes a serious threat with two very powerful STABs with no concern of recoil. For stat boosts, he would obtain two small boosts in Sp. Def and speed, along with a boost to his Attack, but a small drop to his Defense. The defense swaps are a result of his visual loss of armor. Rock Polish gains a new use, while the large buff to Attack makes earthquake hit hard even when not a STAB.
When I came across this beauty, I had an ignited desire to see a Mega Ambipom. This is a very beast design. Through mega evolution, Ambipom would become a Normal/Dark type, meaning while it gets a four times weakness to Fighting, it gets STAB Sucker Punch and another pure resistance, in psychic. For stat changes it gets two great boosts in Attack and Speed and a small boost in Defense, but a cut in Sp.Attack, rendering it completely useless.