I like the fairly recent Stanley 10-016 OTF model for serious use. They're very similar to the ubiquitous Stanley 99, except it's shorter, less girthy and more easily pocketed. And they're really cheap at Walmart. Less than $2.
Of the Superknife-type knives, the best I've found is the Superknife SK2. It's distinguished by the low ride pocketclip and the thumbdisc that doubles as tool-less blade latch. Curiously, these can often be picked up very inexpensively in red or blue. I've found these better than the other Superknives and most other large folders of linerlock and lockback variety. All of these folding type utility knives seem a bit prone to falling apart. Some much worse than others. If you have no problems tightening screws, they can be pretty good.
The Gerber is perhaps most elegant. Very small and compact, it's more like a gentleman's folder/money clip than utility knife. Gerber recently released a new version of the EAB with a skeletonized handle.
