Is there a word (or words) for a person who uses all resources to the maximum; for example, a person who keeps on using pencils even if they are very small?
characterized by or reflecting economy in the use of resources ~ Dictionary.com
By being frugal, he's able to make his box of pencils last a very long time.
avoiding waste or extravagance; thrifty: ~ Dictionary.com
He is economical by nature. He can make a box of pencils last a year.
1. using money and other resources carefully and not wastefully.
he had been brought up to be thrifty and careful
"Thrify", "frugal", and even "economical", while good answers to this question, unfortunately have come to carry negative connotations, in that they're often seen as euphemisms for "cheap", "stingy", or "miserly".
"Provident" is another antonym of "wasteful". It is defined by Merriam-Webster as "making provision for the future : prudent" and as "frugal, saving". It is not as commonly used as most of its synonyms, and perhaps for that very reason, does not bear the same negative connotations.
(Unless, of course, the questioner actually wants negative connotations, in which case I'd recommend "miserly".)
Have you considered the word "exploiter" as a synonym for a person who uses resources to the maximum? Exploiter does have a negative connotation, certainly. See the verb-form definitions here: http://www.merriam-webster.com/dictionary/exploiter. Also, the word "uses" is open to various interpretations. "Uses" can mean "consumes" or "exploits", perhaps, or am I far from the intended meaning of the question?
Most terms I know for this refer to the economic/monetary context of the behavior, essentially equating it with "not spending": frugal, economical, thrifty, penny-pinching/er, tightwad, skinflint, cheapskate, pinchfist, cheese-paring/er1. I suppose that there may people who maximize their resource utilization for reasons other than to save money. Some possible such reasons, all unconcerned with saving money: 1. concern over depletion of the world's natural resources (ecology-minded/aware, resource-preserving); 2. a personal ethical stance towards consumption ("I shall drain the cup to the dregs"); 3. a form of obsessiveness (retentive); 4. a primary repugnance (or phobia) towards waste (waste-averse/phobic).
1 All the italicized terms in this list are generally considered both colloquial and derogatory.