Gleeok

Gleeok in The Legend of Zelda
The Gleeok makes three appearances in the first game. All are defeated in similar fashion. Using the sword, cut off each of the heads on the beast. Once a head is detached from the body, it will float around the room shooting fireballs at Link. Avoid the fireballs and cut off the other heads and the Triforce piece is yours.

A two-headed version of the beast guards the fourth piece of Triforce, a three-headed version is a mini-boss in the sixth underworld, and a four-headed version of the beast guards the final piece of Triforce

Gleeok in Oracle of Seasons
The Gleeok within the Oracle of Seasons is a two-headed version. It is defeated in a different fashion from its former counterpart. Getting rid of the beast's heads is still the main objective, however, there is one more step before defeating it. Slashing away the head is a harder task, more slashes of sword will detach the heads. Once the heads are detached, the beast will start jumping, causing a massive earthquake in the arena. Using the Roc's Cape is the only way to avoid serious damage from the beast. When the beast is grounded attack with the sword. Continue until he is defeated. He will then give up the Seed of Life, the seventh Essence of Nature

The Minish Cap
Though "Gleeok" is not seen in The Minish Cap, the boss Gleerok is a Gleeok with a rock on it's back. (This information is from the figurine.)