I'm a bit biased towards Heracross, during a Nuzlocke run in HeartGold, I got headbutt from the guy and used Heracross as my encounter for Azalea. I found a tree and crossed my fingers and to my absolute amazement, a Lv.5 Heracross popped out.
After catching him on the first throw, to my amazement he fucking just happened to be adamant nature, which was amazing. Incidentally, I put him to sleep before catching with my Gastly which was modest natured catch from sprout tower. Both of them were perfect natured and survived for my entire run, but Heracross was the greatest bro, when he got Megahorn, STAB boosted was great for neutral hits and bug does hit some unique types, plus flying type move demolished Chuck and Brick Break/Close Combat smashed everything else into submission. As well as another coverage move I can't remember to hit anything else neutrally. He was absolutely great.
His design is the tops too, it's very understated and simple, but it works perfectly. He epitomizes what pokemon is, as its influences from both bug catching/the weird Japanese hobby of making horned bugs fight. He's not too popular as to having hipster-ish people shit on him all the time and there's no "edgy" or whatever look about him... and has decent usage competively.
