When I was talking to a friend he said that in his party his fighter uses gnome chucks. And I was wondering if anyone else uses this weapon in their campaign. And what damage would this weapon do?

Probably referring to nunchuks (or nunchaku). Flavor-wise, think Michelangelo from teenage Mutant Ninja Turtles. Stat-wise, I'd call it a club, 1d4 + modifier.

Yes, but you tie down two gnomes together with rope and use that as a weapon

This immediately sounds to me like it should be some sort of catapult called "the Gnome-chucker."

...now I have to write siege weapon stats.

Carrion

Quote from BillPill >>

Yes, but you tie down two gnomes together with rope and use that as a weapon

 Well if no one was using them in a game, they probably will now.

In that case my question is... what weapons do the gnomes have? :)

Quote from Maestrino >>

In that case my question is... what weapons do the gnomes have? :)

Daggers, of course. Or metal claws on their hands and feet.

Quote from Maestrino >>

In that case my question is... what weapons do the gnomes have? :)

 More gnome chucks, of course.

(Don't even ask what weapons those gnomes have.  It's all gnomeception from there...)