Buying used things certainly saves money.  For example, the price of a new music CD can easily reach to $15 or $18 depending on the CD and the store; in comparison, a perfectly playable CD in a used music store sells for about $5 to $8 and that same CD in a pawn shop can be had for $2 or $3.  Similarly, a guitar pedal that retails for $100 (and can only be found in overpriced music stores) normally sells on eBay for about $25 in perfect working order.  It isn't all that uncommon to find most used items costing 25% or less compared to the price when bought new.

Buying used items reduces waste.  By buying a used item, one saves it from living in a landfill for the next ten thousand years and reduces the demand for new items.  This in turn reduces demand for raw materials and thus reduces the depletion of nonrenewable resources and the environmental impact of manufacturing new items.  That's something any tree-hugging environmental activist can appreciate.

Buying a used item to give as a gift can show that you cared enough to think about the gift that you were buying.  It shows that you took enough time to learn about that particular field of interest and learn that a used item is just as acceptable as a new one.

Sometimes the only way to acquire a certain item is to buy it used.  For example, it's nearly impossible to find an antique that hasn't been used.  Nowadays, it's also very difficult to find affordable hardwood furniture, but used furniture can be acquired at reasonable cost, and even refinished, skills and time providing.

It does take a little more effort to find used items.  In several areas, stores have found niches in the used market.  In others, more searching is required.

Of course, one must exercise judgement when buying used things; no one would buy a used pair of underwear or a used box of chocolates.  It is perfectly reasonable, however, to buy a used car or a used musical instrument.  If in doubt as to whether or not it would be appropriate to buy a used item instead of a new one, do more research.  A couple hours of reading should certainly resolve that issue.  In any large purchase, a modicum of research is required anyway; that's part of fiscal responsibility.