Response: Choosing the best moveset for Greninja in Pokémon X depends on your playstyle and the competitive or casual nature of your battles. Here are several effective movesets that you can consider:

### 1. **Special Attack Moveset**
This moveset is ideal for those who want to focus on special attacks and utilize Greninja’s high special attack stat.

**Moves:**
– **Hydro Pump** (STAB, high damage)
– **Dark Pulse** (STAB, coverage against Psychic and Ghost types)
– **Ice Beam** (coverage against Grass and Flying types)
– **U-Turn** (switching move with damage)

**Item:** Expert Belt or Choice Scarf
**Ability:** Protean
**EVs:** 252 SpA / 252 Spe / 4 SpD
**Nature:** Timid or Modest

This set is versatile and can handle various opponents effectively.

### 2. **Physical Attack Moveset**
This moveset is suitable for those who prefer physical attacks and want to utilize Greninja’s high attack stat.

**Moves:**
– **Night Slash** (STAB, high damage)
– **Waterfall** or **Water Shuriken** (STAB, priority move)
– **Aerial Ace** or **Rock Slide** (coverage against Flying and Rock types)
– **U-Turn** or **Power-Up Punch** (switching move with damage)

**Item:** Focus Sash or Choice Scarf
**Ability:** Protean
**EVs:** 252 Atk / 252 Spe / 4 HP
**Nature:** Jolly or Adamant

This set provides a good balance of physical attacks and can handle Dark-type moves effectively.

### 3. **Versatile Ninja Moveset**
This moveset combines special and physical attacks, making it versatile for various battle scenarios.

**Moves:**
– **Hydro Pump** (STAB, high damage)
– **Dark Pulse** (STAB, coverage against Psychic and Ghost types)
– **Extrasensory** (coverage against Toxapex and other Psychic types)
– **Ice Beam** (coverage against Grass and Flying types)

**Item:** Expert Belt or Choice Scarf
**Ability:** Protean
**EVs:** 252 SpA / 252 Spe / 4 SpD
**Nature:** Timid or Modest

This set ensures that you have a move that is super effective against most types of Pokémon.

### 4. **Ocean Master Moveset**
This moveset focuses on Water-type special attacks, which can be very powerful with the right setup.

**Moves:**
– **Hydro Cannon** (high damage)
– **Surf** (STAB, high damage)
– **Water Shuriken** (priority move, high damage)
– **Rain Dance** (setup move to increase Water-type move power)

**Item:** None
**Ability:** None
**EVs:** 252 SpA / 252 Spe / 4 SpD
**Nature:** Timid or Modest

This set is ideal for those who enjoy using Water-type special attacks and want to maximize their power.

### 5. **Hands-Off Moveset**
This moveset focuses on Greninja’s Protean ability, allowing it to change its typing based on the move used.

**Moves:**
– **Gunk Shot** (coverage against Fairy types)
– **Rock Slide** (coverage against Rock types)
– **Low Kick** (coverage against Normal types)
– **U-Turn** (switching move with damage)

**Item:** None
**Ability:** Protean
**EVs:** 252 Atk / 252 Spe / 4 HP
**Nature:** Jolly or Adamant

This set is versatile and can change its typing to counter various opponents effectively.

### Conclusion
The best moveset for Greninja in Pokémon X depends on your specific needs and preferences. If you prefer special attacks, the first set is ideal. For physical attacks, the second set is better. The versatile ninja set offers a balance between both. The Ocean Master set is great for those who enjoy Water-type special attacks, and the Hands-Off set leverages Greninja’s Protean ability for maximum versatility.