Goofy uses Shields as his weapon, blocking enemy attacks and dishing out his own by ramming into enemies.  Shields offer surprising strength increases considering they are a primarily defensive weapon.  Each Shield is fully detailed below, listed in alphabetical order.

Adamant Shield

STR: 5
Size: Large
Buy: 4000
Sell: 260
Obtained: Item Shop (Traverse Town)

Defender

STR: 13
Max MP: +1
Size: Large
Sell: 1000
Obtained: Dropped by Defenders

Dream Shield

STR: 6
Max MP: +2
Size: Medium
Obtained: Speak to Merlin after acquiring every kind of Spell Arts from the White Mushrooms (Traverse Town)

Genji Shield

STR: 10
Size: Large
Obtained: Clear Seed 44 in the Hades Cup (Olympus Coliseum)

Gigas Fist

STR: 7
Size: Small
Buy: 1000
Sell: 200
Obtained: Item Shop (Traverse Town)

Golem Shield

STR: 3
Size: Large
Buy: 1000
Sell: 200
Obtained: Item Shop (Traverse Town)

Herc’s Shield

STR: 9
Size: Medium
Obtained: Win the Hercules Cup (Olympus Coliseum II)

Knight’s Shield

STR: 1
Size: Medium
Obtained: Default

Mighty Shield

STR: 15
Obtained: Treasure Chest in the World Terminus (End of the World)

Mythril Shield

STR: 4
Size: Medium
Buy: 750
Sell: 160
Obtained: Item Shop (Traverse Town)

Onyx Shield

STR: 6
Size: Medium
Buy: 2800
Sell: 220
Obtained: Item Shop (Traverse Town)

Save the King

STR: 11
Max MP: +2
Size: Large
Obtained: Win the Hades Cup Time Trial (Olympus Coliseum)

Seven Elements

STR: 4
Max MP: +3
Sell: 300
Obtained: Synthesize at the Moogle Shop (Traverse Town)

Smasher

STR: 3
Size: Small
Buy: 250
Sell: 90
Obtained: Item Shop (Traverse Town)

Stout Shield

STR: 1
Size: Large
Buy: 250
Sell: 90
Obtained: Item Shop (Traverse Town)