Tools are items used for some utilitarian purpose. Strangely, tools are often either very light, or very heavy.
One of the most useful tools in the game; pick-axes are mostly used for digging shortcuts through dungeon walls and mining for valuables. A Scroll of Detect Material will help keep you from having to mine every single square of a dungeon level to find all buried treasures.
♫Dig a tunnel, dig-dig-a-tunnel...♫
Harder walls and dirt require a harder pick-axe; an Octiron pick-axe will be plenty good enough for the majority of the game. By the time you need something harder than that, you'll have much more pressing issues than looking for pretty rocks.
While they may seem a bit out of place in a world of swords and magic, stethoscopes are quite useful for seeing the stats of literally anything that moves. They are also great for checking yourself for diseases or states you can't normally see on your right sidebar, such as Confusion or Teleporting. Even hostile creatures can be examined; apparently even Sherarax will pull up her shirt and take a deep breath for you. ;)
Using a stethoscope is very quick; feel free to examine your enemies mid-combat without much fear of reprisal.
Horns, lyres, whistles can be found and played. See here for a full article.
Used for bringing light were there was none before, light source is a must for every adventurer. Most dungeons are fully dark except for small illuminated rooms and thus you have to carry your own light. The first thing most players will pick up is a lantern in the entrance room of Underwater Tunnels.
See here for a full article.
Useful to bring quick demise to your enemies, they can unfortunately also backfire spectacularly and bring death to you.
- Palm branches are used by Female Servants to fan their masters.