Hey fellow Final Fantasy X explorer! When it comes to side quests, there are a few key ones you definitely don’t want to miss.

1. **Monster Arena:** By capturing monsters throughout Spira, you can unlock the Monster Arena side quest. It’s a great way to test your skills in battle and earn some fantastic rewards.

2. **Celestial Weapons:** Each character has a unique Celestial Weapon that is incredibly powerful. To unlock their full potential, you’ll need to complete challenging side quests specific to each weapon.

3. **Omega Ruins:** This optional dungeon is not for the faint of heart, but the rewards are definitely worth it. Make sure your party is well-prepared before venturing in.

Remember, side quests can provide you with valuable items, experience, and abilities that can greatly enhance your main game experience. So, don’t be afraid to explore and take on these challenges!