Voice-changing bow-tie - this is the very first gadget which Dr Agasa gives to Conan after his transfiguration, this is the red bow-tie which Conan usually wears. As you can interpret by the name, Conan can use it to imitate anybody's voice. This is a very useful gadget for Conan to solve cases and he always uses it to imitate Kogoro's voice and sometimes Sonoko's. The first time Conan uses it is the murder case at Okino Yoko's apartment.
Stun-gun wrist-watch - this is a watch that contains stun-gun, but it only has one shot each time. Conan uses it to make Kogoro or Sonoko sleep before he uses the voice-changing bow-tie to decuce the criminals. Besides using it on Kogoro, Conan also use it to catch the criminals.
Power assisted kick shoes - these are very powerful shoes that can even make trees fall, so Conan has to use it very carefully while he kicks some material towards the criminals, he usually uses a soccer ball and always has a precise aim.
Conan's balloon-making belt - as the name suggests, this belt can produce a balloon, or a soccer ball in general. Once Conan has pressed the belt button, a ball will be produced~ and the ball can be of any size. This is very useful for Conan when he needs to use something for his power assisted kick shoes. In fact, the ball can only hold ten seconds before it looses all the air
The tracing glasses and sticker - Conan can use his glasses to trace the criminals, and the sticker is the transmitter, so Conan has to stick it on the criminals' clothes to be able to trace them, he is able to see a map and the criminals' locations as he wears his glasses.
(see previous picture)
The eavesdropping glasses and transmitter - This is a listening device, Conan hides the transmitter in a chewing gum and stick it underneath the seat of the men-in-black whom he meets on the train trip, and then he listens to their conversations by wearing his glasses.
Elasticity suspenders - Conan always wears these suspenders, it is very elastic and can open any heavy stuff such as lifting up a car.
((**All desciptions lovingly ripped off of this site:
http://hem.bredband.net/dreamforest/conan/gadgets.htm))