number 2 pencil

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun US A pencil which produces a specific shade of dark gray. One can usually identify a number 2 pencil by looking for the number "2" conspicuously emblazoned on the pencil. Often required for test-taking and the completion of official forms.
• noun US A standard, ordinary pencil; one which is not colored or mechanical or in any other way unusual.