The 3/4oz Victorinox paring knife is one my favorite ultralight finds. The bulk version comes with a simple plastic sleeve and seeing that the serrated blade is razor sharp, a sheath would be a good option. BUT, there is little sense in increasing the weight drastically with a sheath.
Lo' and behold, I was in REI today and looking around the knives and tools, and I spotted the paring knife with a fitted cover. They are calling it a "Little Vickie utility knife."
http://www.rei.com/product/836226/victorinox-little-vickie-utility-knife
$9.00. the knife itself is 0.7oz and the cover adds 0.2oz. These are fantastic knives for food prep and light repairs.


That cover also fits my coveted Forschner plain-edged version with a rosewood handle






