You can surely try to sell anything you want but like anything it comes with a price! Likely the least would be banned and the worse case banned after some sort of undercover cop sets you up for a long term vacation with a man named bubba for a roomate.
My dad accidentally killed my sea monkeys, knocked 'em right off the wall unit. Schmeeeee :-( As for other discreet items, one imagines, wouldn't do well via the mail. Maybe if you just use the site to meet in person; but I imagine the heat's got people watchin boards like this one.