Lost in a sea of better known competition, the T10 Multitool by IDL Tools is a lesser known, but not lesser quality, contender.
The tool is all stainless steel construction, and held together with peened pins. The tool is 2" (51mm) long, 1 1/8" (29mm) wide, and an incredibly thin 5/16" (including pins. Without them, it's only 1/4" (6.5mm) thick. Weight is 1.7 oz (49g).
Here is the tool folded up.