Birch - Craft Pen Knife [More Info]
Scapel blade.

Birch - Handi Cutter [More Info]
Handy Size

Birch - Craft Scalpel Set [More Info]
6 removable blades.

Olfa Compass Cutter [More Info]
Circles of up to 6" in diameter.

Olfa Stencil cutter - double blade [More Info]
Blades 1.5mm apart.