Ayu-mi-x III Non-Stop Mega Mix Version was created on 2001-02-28.
Ayu-mi-x II Version Non-Stop Mega Mix was created on 2000-03-29.
Yes there is a mega version of every weapon excluding the wrench which you can upgrade at vending machines throughout the game.
Mega Force was created in 1989.
Mega Maldives was created in 2010.
Mega - magazine - was created in 1992.
Mega-Carrier was created in 2005.
Mega Apocalypse was created in 1987.
Mega Society was created in 1982.
Mega Twins was created in 1990.
Mega Brands was created in 1967.
Mega Zeph was created in 2000.
Mega Zone was created in 1989.