Removing Utility Sink

I have a utility sink in a closet that I desperately want to remove and replace with shelving. What do I do with the water pipe once the sink is gone? Is there something I can cap it off with?

Yes. How about some picture for us?

Without knowing more particulars, it's hard to give specific advice, but here are some general pointers. You have two things to deal with. Water supply lines and the drain. You could just cap off the ends of the supply lines and leave the stubs ends showing in the closet or you could go to where they branch off of the main supply lines, remove the pipes from the closet to that point, and cap at that point. What to use depends on what kind of pipes you have. Copper, galvanized, or plastic pipes all require their own materials. The drain also can be capped by removing the P trap and plugging the line at that point or by removing the drain line down to the point where it is attached to the main drain. Again there are different pipe materials to deal with. Galvanized, copper, plastic, or cast iron are the common drain pipe possibilities and they too have there own requirements as to the exact way and materials to use. You could also cap off these lines within the wall so that they would not be seen. Obviously, the more you take out, the more the job becomes a carpentry job more than a plumbing job.