I don't have faith in my ability to create a weapon from scratch, but I CAN tweak them. This is me screwing around with Classes and making them beyond ridiculous, and let me tell you, it was fun to do :D . Not only that, but I also messed around with the Extraweps and 3 MM8BDM weapons (can you find them?) The tweaked classes I remember off the top of my head are:
Megaman
Bass (Also, use his Treble Boost :D )
Quickman
Sparkman
Geminiman
Docrobot
Snakeman
Drillman
Diveman
Napalmman
Gravityman
Chargeman
Crystalman
Centaurman
Freezeman
Turboman (barely)
Download here. (http://www.mediafire.com/?pcdcskflk2xy3gx)
If there's other I'm forgetting please tell me so I can update the list.