Chunk

""He (Buzz) ain't the sharpest knife in the... uh.. place where they keep the knives! Neither are you, Chunk!""

- - Sparks mocking Chunk (also the only time in the film where Chunk is mentioned by name).

Chunk is one of the (former) quaternary antagonists of Toy Story 3. He is a large rock monster toy who has two emotions, happy and mad. He's one of Lots-O' Huggin' Bear's henchtoys.

He is voiced by Jack Angel.

Toy Story 3
Chunk made his first appearance where Andy Davis's toy enter Sunnyside. Chunk was in the crowd once the Jack-in-the-box said "New toys!". He is seen shaking Jessie's hand. Later, Chunk was seen on the interior of the vending machine where they are playing poker (See-'n-Say) Chunk got very mad and shouted that Ken was a girl's toy and Ken was mad. Chunk and Sparks later seening trying to imprison Jessie, however she kicks them both in the face. Chunk was later seen in one of Lotso's minions and during the confront, Chunk had his mad face. Chunk later reappeared in the end being reformed during the credits.

Toy Description
From Official Website:

"Chunk will rock your world! This gargantuan creature sports protective shoulder spikes, while his ferocious fists are ready to smash whatever enemy gets in his way. Chunk's oversized limbs are fully posable, making him ready for hours of imaginative fun. As an added bonus, the press of a hidden head spike will spin Chunk's expression from friendly to fierce! No batteries necessary."

Trivia

 * Chunk appears to be based on the short-lived Rock Lords toyline from the 1980s.
 * Many of the Chunk toys created have the face feature. However, some have it changed by pressing the spike on the top (as seen in the picture below toy description), and the others have it changed by swiveling his face.