Pickett Circle Master Inking Template No. 12041, which is handy for nice, clean circles.
Faber-Castell E-Motion 1.4mm mechanical pencil. I love the soft B lead, as it lets me get shades down on paper quickly, yet lets me draw pretty fine lines off the edge of the lead.
Kneadable erasers are great, because they can be formed into any shape you like, and work well as stress relievers.
Y&C Grip 350 0.7mm mechanical pencil is wonderful for tight lines, yet is thick enough to hold up to quick sketching. I especially like that the tip restracts into the barrel for safe transport in gear bags and pockets.
My Artec1031 6" clear acrylic triangle is small enough to carry anywhere, helps me make crisp lines. The clear plastic is nice for seeing through to my sketches.
My Miquelrius A5 squared notebook is flexible enough to fold either cover over for sketching or scanning, and the squared pages make for handy guides when drawing lines and right angles used in web and print design.
My HiG A4 squared notebook from Germany is a nice size for larger sketches — generally used for website designs, print design work and storyboards.