Well, I don't really have any ideas for weapons, but sort of...
Like, in Jazz3 I would like Jazz and other characters to have different weapons that look different, and perhaps you can't move as fast with some. For example, if he has a big bazooka, it would LOOK like one first of all, and he would have to move much slower. But the damage to enemies would be greater, so you decide if you want to take that risk or not. I guess I just think it's kind of lazy to have Jazz have the exact same blue gun that just shoots out different ammo. It can be different VARIATIONS of that blue gun, like the gun could kind of transform into another gun - that would be cool, and you could move differently, or reload or whatever. Think about "Conker's Bad Fur Day" if you've ever played it on N64. And there could be close-range weapons like a chainsaw or something. Don't know whether this game should be grewsome or not. Wouldn't hurt it for sales I think.

Maybe there could be a weapon that does some random thing to your victim. It makes them go slower or not be able to shoot, or be frozen - etc. Or that could be some kind of environment thing.

Oh, and in JJ3, should enemies be like in Jazz 1 and 2, or should they have weapons too?