One of those nifty cable to any rare filters--just read
 

I know they are all clientsided and crap but someone needs to make one where you can trade the rare you chose, it looks real in the trade box, but once they agree, it looks normal in their bag but once they reload coke or put it down and reload it turns back to the normal norm......

its possible but they would have to activate a filter of their own for them to see the clientside rare.