Personally, I like to use a variety of things. Rope, of course, is something of a mainstay, but it also requires a great deal of skill and patience to use well. I personally have not mastered it, and sometimes I'm in something of a hurry. But I think it's hard to deny that some of the best, most artistic bondage is accomplished primarily by means of rope.

In general, I'm a big fan of using different devices in tandem in order to hold my sub in place. For example: attaching a rope to her hair that runs through her legs, and up to a chain between her nipple clamps. Or: tying her on her back, but leaving her head loose, but putting a non-drip candle in her mouth (non-drip candles still produce wax when not held at a right angle). She's not blindfolded, but if she tries to look up to see what I'm doing, she'll get wax on her neck. I could go on, but I think you get the idea.

As far as leather, or metal, or other tradional restraints go, I don't have too much experience with many of those. I'm still too much on the move to have settled down and established a dungeon of any kind (I work out of a bag), so transportability is a must still. That said, I can't imagine getting by without handcuffs, or a good collar.