One of the best platformers I seen on NG.
This game is awsome. Great controls, nice amount of weapons, collectibles, and challenges. There's some Cons, but not bad enough to not give 10/10. XD
-Some speed challenges seems too difficult to do, specially Rattlers Ravine and I don't see how Deadridge Railway's is even possible.
-80 badges seems awsome at first, but way too many were "kill X many enemys with Y weapon". It's not bad if it was just ones like TnT barrels kills, the chickens, the squirt gun, pistol shoot pistol weilders, etc. But one for each weapon seems unneeded.
-A boss every few levels would be nice, though not needed.
I don't see any improvements you need to make for a sequel, besides the usual "more levels" thing. XD Maybe a way to recover health would be nice with health upgrades. Maybe even a tumbleweed/dog hybrid companion? :P
If you make any NG medals, might I suggest don't use all the "killing X many enemys with Y weapon" badges for them, just put a "Get all weapon kill badges." medal in their place.