Tire - male, because it goes bald and often is overinflated.
Sponges - female, because they are soft and squeezable and retain water.
Hammer - male, because it hasn't evolved much over the last 5,000 years, but it's handy to have around.
Kidneys - female, because they always go to the bathroom in pairs.
Ziplock Bags - male, because they hold everything in, but you can always see right through them.
Web Page - female, because it is always getting hit on.
Shoe - male, because it is usually unpolished, with its tongue hanging out.
Remote Control - female, because it gives men pleasure, he'd be lost without it, and while he doesn't always know the right buttons to push, he keeps trying.
Swiss Army Knife - male, because even though it appears useful for a wide variety of work, it spends most of its time just opening bottles.
Copier - female, because once turned off, it takes a while to warm up, it is an effective reproduction device when the right buttons are pushed, and because it can wreak havoc when the wrong buttons are pushed.
Hot Air Balloon - male, because to get it to go anywhere you have to light a fire under it... and of course, there's the hot air part.
Hourglass - female, because over time the weight shifts to the bottom.
Subway - male, because it uses the same old lines to pick people up.
Can you spot the female duck?