Do you need an Aperture Science Handheld Portal Device? Of course you do! Sure, there's a life-sized replica out there in the world, but for those of us with smaller living rooms (and smaller budgets), this miniature edition, from ThinkGeek, is just the ticket.
This model, admittedly, can't actually make a wormhole in your wall. But it does come with the lights and sounds you need to feel like it actually works.
You could even put a potato on those arms. A baby potato, admittedly, but still.