Spyderco Ladybug 3 Lightweight Purple
 
It attaches to your keychain and is nearly as small as your car keys, One of Spyderco's smallest lightweight knife is the Ladybug.
 
Made of VG-10 stainless steel, the hollow ground blade comes in a PlainEdge configuration. This modified clip-point blade style is matched up with a purple, lightweight handle of fiberglass-reinforced nylon making the entire knife weigh only 0.6 of an ounce (16.4 grams). The Ladybug doesn't have a clip but rather a lanyard hole for attachment to a keychain or lanyard. 
 
Like its larger counterparts (and all Spyderco knives) the Ladybug3 packs tremendous cutting power and can take on both fine and heavy cutting tasks.