I usually try as well. Sometimes it works, more times it doesn't. It almost always comes with an odd look or the great big "you just added a lot more work to my day" sigh.
I usually go after the "last years model" or "clearance" type items, iphone in hand to demonstrate the current retail value. The most they'll ever do is knock a few percent off and offer me a free cable or something. Their best offers are almost always still ludicrously beyond the reasonable current price. Trying for more gets us a little session at the Altar of the Wyse Terminal, followed by a shrug and "It won't let me do that". Even when the manager is involved.
I'm hoping that bargaining in retail stores will become both common, fruitful, and a socially expected norm.
I don't think it's likely. It doesn't scale to the transaction volume of a department store. Imagine you're in the checkout queue at Walmart and the person ahead of you is trying to bargain with the cashier for 20 minutes to try to save a few dollars.
My favorite haggling technique is to ask about the credit options and extended warranty.
If you're going to haggle, act like you're going to buy it on the store credit card with extended warranty.