Mop? ...Kind of like being flicked with a wet towel, I'd imagine.
Yuffie's pinwheel and Aeris' Umbrella look innocently novel; the Nail Bat makes Cloud look like a thug (not necessarily a bad thing).
one of clouds earlier weapons, i forgot the name, but it is black and it has all of those points, it just looks plain out wicked, well lets see, i beleive i got it on that mountian, it may as well be the relic but dont quote me on that...
Force Stealer, perhaps?

Vincent's Shotgun is a nasty piece of work.

Yuffie's weapons usually look pretty interesting - the Conformer, Oritsuru, Twin Viper and others.

Cid's Venus Gospel has a beautifully designed blade. Huge, but shiny and ornate.

Somewhat like the Ultima Weapon. I like the way its blade becomes a duller shade of blue as the Cloud's HP - and the weapon's strength - become lower.
The Buster Sword, however, has simple functionality in its favour. It's a solid, dependable, in-your-face design which looks like it means business.

Dang, but there are so many interesting weapons in FFVII, hardly any which DON'T stand out in some way.