Lmao I like the Gelato being ice power idea. Gelato for ice and pizza for fire would be hillarious. I LOVE that idea for the pizza too like, you can have different toppings like contra power ups that effect the projectile lmao. I also like the guitar idea.
MORE IDEAS

(I love ideas)
Boomerang: long distance can get items and hit switches, maybe also have boomerang puzzles like "the annoying stick" game where you have to stay in the lines
Batton: Good old short range melee. Can be used to get past rythem parts of the game where you have to tap tap revolution style it. Maybe one part a fight happens between a different member of the wario ware crew and mona has to button mash to cheer for them so they can beat enemy arse.
Guitar: (token sound attack suggestion and same suggestion as above rythem game suggestion only this time its laid out guitar hero style). Maybe it can also be a mid range melee weapon capable of sending out musical notes to attack but by being smashed on enemies it breaks slowly (Punk rock style like when they smash their guitars).
Moped: Can be an ability (maybe even unlockable) that is like monas version of wario's dash attack. Maybe when she pulls it out she can even stand on top of it to create a sort of platform on the go. Might be able to cross over some terrain mona can't normally.
Camera: stun enemies? take pictures of enemies for some sort of enemy/location/item catalogue PERHAPS a different wario ware character is having mona collect (thats a good way to throw in more characters)