If there was one Pokémon that need a Mega Evolution back when they were doing that, it was Dunsparce.
Nidorina! Everyone clamours over Nidoqueen and Nidoking, but Nidorina has always been my favourite. She is really cute and huggable, but she can also be awesome! She had my favourite colour in the whole world too!
Liepard is amazing speed house with access to play rough and tbh i don't hear much from that cute kitty but that can also be said about stoutland and most of the two evo lines like watchog, furret, linoone or Pokémon like zangoose and absol. Sure they look cool but because they are not Garchomp or T-tar they are not too viable and there for not looked at. Heck you can look at Smogons PU section and bam people ignore those babes..I can go on and on about some great Pokémon that are never used because of the Lucario's Garchomp's Blazakin's etc trolling the yards in popularity, Mega evolution also did not help this. i shall now leave my squishy arceus killer here[3D='423']
Sigilyph. A lot of people dismiss its weird design (and I have to admit, I did too) but once I used it on my team, I was amazed at how useful it was. Its Magic Guard ability saved it from the effects of hail and sandstorms and its high speed and special attack proved incredibly useful. It's now my favourite psychic type!
I think wooper could get more credit for being a perfect axoltyl colour when shiny :'D and being cute regardless. Also think cherrim is a great design that doesn't come up often (I'm guessing it's not very practical).
There are a lot of supposedly 'ugly' Pokémon designs that I actually think are kind of awesome, but the two that stand out for me the most are Palossand and Barbaracle. Barbaracle especially I always thought looked awesome the minute I saw him as he reminds me of something straight out of the Kinnikuman franchise. Also, Gamefreak, can you please start making official evolutions for older Pokémon so Dunsparce can have an awesome second form already? Seriously, I see so much wasted potential with this one.
I'd say the zubat evolution line. A lot of people give it hate for being so common and often annoying to encounter in the wild, but crobat is incredibly useful and I've used it in my main team heaps of times.
I think Magikarp is the most underrated. Yes, it doesn't do much more than flopping around, but it's a great choice for a gym battler.
What about Smeargle? I used to think it was stupid and had no place in the Pokémon world, but then I read about using it for shiny hunting... and now I can't stop thinking about it. Sketch is such a wonderful move, and should be taken advantage of.
I think Wobbuffet is such an underrated Pokémon, both competitively and not. Ever since the ban of Shadow Tag in Smogon's tiers, it hasn't had much time to shine