Aquamentus
The first dungeon Boss that Link is likely to encounter. A dragon that shoots fireballs that split in three directions and can only be blocked by the Magical Shield. Vulnerable to the Sword and Arrows. Can also be killed by three bombs.
Digdogger
Sea urchin boss. Appears as a large yellowish circle with an eye in the middle. Blowing the whistle will cause Digdogger to split into as many as three smaller parts which can be defeated with the Sword.
Dodongo
Slow-moving rhinoceros boss. Often appears in groups, they are only vulnerable to the Bomb. An effective tactic is for Link to place the bomb directly in front of Dodongo's mouth. Each Dodongo will be defeated after eating two bombs, but you can also stun a Dodongo if you can make a bomb go off in it's face. If you do, he will be stunned and temporarily vulnerable to an attack from your sword.
Ganon
The final boss. Capable of becoming invisible and moving around the room. Link must use his judgement and stab at the place where he predicts Ganon will materialize next. After wounding him enough, he will become stunned and visible. Then only a single attack from a special weapon can do him in and allow Link to save the Princess. Without this weapon, Ganon will gain his strength back and continue his assault on Link. The weapon can only be found in the final dungeon, but can Link locate it?
Gleeok
Recurring underworld boss. A dragon with two, three or four heads, Link must attack each head. When a head takes enough damage it detaches from the body and flies around the room, continuing to attack Link. The flying heads are not vulnerable to attack, so dodge their projectiles and focus on the attached heads.
Gohma
Crab monster boss. It's large central eye is its only weak spot. He normally keeps the eye closed, but opens it breifly from time to time. That is your chance to attack it with its only vulnerability, the arrow.
Manhandla
Four-armed plant boss. Moves slowly at first, and then more quickly as it loses arms. While it is vulnerable to the Sword, it is possible for one well-placed bomb to defeat this boss in a single stroke. A less direct hit will at least sever one or more arms.