How about this one?

In Contra and Super Contra NES games, when you press SELECT you change your holding weapon anytime.
BTW (F)ire gun in Super Contra are diffrent from first Contra game.
If that possible let have them selectable in both games.

List of weapons

Rifle aka default gun(Slow firing limited white bullets)
(M)achine gun(Fast firing red bullets)
(S)pread gun (Three wide firing red bullets)
(L)aser gun (Single laser beam)
(F)ire gun  (Multi circle pattern firring red bullets)
(F)Fire gun(Super C version) (Single big ball when hit something explodes in small ones)