Leap. The Giant Squirrel leaps up into the air to get out of harm's way. This way it can also attach itself to a wall or ceiling. In addition, if it has grappled a creature, the Giant Squirrel will take it with them. The climbing speed while holding on to a surface is 30ft.

Multi-attack. The Giant Squirrel makes 3 attacks with its Claws, one with its claws and one with its Tail whip or one with its claws and then with Magic acorn.

Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 5 (1d8 + 2) slashing damage. 
The squirrel attacks with its claws, slashing any opponent that stands in its way.

Tail whip. Melee Weapon Attack:  +5 to hit, reach 10 ft., multiple targets. Hit: 10 (2d8 + 2) bludgeoning damage. Additionally, the target(s) must make a DC12 Dexterity ST or get knocked back 10ft.
The squirrel smashes one or multiple opponents with its tail. It might look fluffy, but getting hit by it still packs a mean punch!

Magic acorn. RangedWeapon Attack: +6 to hit, range 10/ 120ft., 1 target. Hit: 5 (1d10 + 3) bludgeoning damage and 1d6 elemental damage from a random element of the table below.
(1d6)
1 - Thunder
2 - Fire
3 - Cold
4 - Necrotic
5 - Acid
6 - Radiant
Due to the magical experiments performed on it, the squirrel summons magical acorns out of thing air. On top of the damage of getting hit by one, it also deals extra elemental damage. Watch those trees!

Acorn's hat. If the Giant Squirrel hasn't used its Magic acorn attack in its last turn it can use this reaction to summon an acorn as a shield and add +3 to its Armor Class. Additionally, if the attack is of a certain element you can use the random element table specified in the ability to negate all damage.