Devil Fruits are both a blessing and a curse in the world of One Piece. While they potentially bestow awesome and useful abilities, they also doom the person to a life out of the water. Devil Fruits aren't the only way to grow strong in the world of pirates, and there are plenty of characters who can hold their own without any abilities.
Zoro is a master swordsman and has honed his body and skill to the point where he can clash against most Devil Fruit users and come out on top. While there are plenty of fruits that would just be a detriment to him, there's also some that might just give him an extra edge to become the strongest swordsman.
10 Love: Diamond Diamond Fruit
The Diamond Diamond fruit allows the user to turn any part of their body into a diamond. If this fruit is combined with Zoro's armament Haki, he'd be almost impervious to damage. This is perfect for the swordsman, as he could then focus all of his energy on attacking instead of wasting time with defense.
Even if the diamond makes him heavier and slower, Zoro has trained his body extensively and could easily adapt. His fighting style relies more on strength than speed anyway.
9 Hate: Clear Clear Fruit
The Clear Clear fruit allows the user to turn themselves and other objects invisible at will. While many swordsmen would leap at the chance to get this fruit, Zoro is not one of them. Zoro fights with a swordsman's honor code, and would only stoop to a sneak attack if it would save his friends.
Zoro would simply never use this fruit if he got it, and would actually consider it a hindrance considering he'd lose the ability to swim for no real reason.
8 Love: Dice Dice Fruit
The Dice Dice fruit allows the user to turn any part of their body into blade-like steel. While Zoro rarely goes without his three swords, there have been times where he had to fight without them. Turning his body into a blade would be very exciting for him, and many of his techniques would likely translate over.
Being armed at all times is perfect for Zoro, and would possibly lead to a new four sword style. Combined with his Armament Haki, he would be a force to be reckoned with.
7 Hate: Barrier Barrier Fruit
The Barrier Barrier fruit allows users to create incredibly strong defensive barriers that they can move and shape at will. While this is a powerful Devil Fruit, it would be worse than useless for Zoro.
Zoro would have to use one or both hands to form the barrier, meaning he'd be fighting at less than full strength. Zoro is also an attacker, not a defender. He's not one to stand back and try to keep people safe. He will go after one of the strongest opponents and make sure that they can't hurt his friends. The Barrier Barrier just isn't for Zoro.
6 Love: Arms Arms Fruit
The Arms Arms fruit allows the user to turn their body parts into various weapons. While Zoro wouldn't even come close to using this fruit to its full potential, he would still absolutely use it to form blades from his arms or fingers.
The ability to use his sword techniques without a sword is infinitely useful to a man like Zoro. He'd never use it to make anything like a gun, but he doesn't need them anyway. He's trained in the way of the blade, so that's how he's going to use this fruit.
5 Hate: Human-Human Fruit
The Human-Human fruit allows the user to take the form of a human. While this is incredibly useful for a reindeer like Chopper, it would be utterly useless for Zoro. It would essentially be a fruit that just gives him a weakness to water.
There's not a single pro for Zoro to want to eat this fruit, and he would avoid it at all costs. Zoro desires to be the strongest swordsman in the world, and he isn't going to do that by picking up weaknesses for no reason.
4 Love: Onigumo's Unnamed Devil Fruit
Onigumo's fruit appears to be a spider Zoan, allowing him to produce six additional arms at will. While Zoro uses the three sword style, that would quickly change if he got this Devil Fruit.
Zoro could master an eight sword style, which would be perfect since he is trying to collect the legendary blades. There are more than three blades, so unless Zoro wants to just leave them on a shelf this fruit would be a great fit. He could wield eight legendary blades and become an even more elite swordsman.
3 Hate: Venom Venom Fruit
The Venom Venom fruit allows the user to turn their body into venom as well as control it freely, and its potential was shown at great lengths by Magellan. While it's an incredibly strong ability, Zoro would absolutely refuse to use it except in the direst circumstances.
Zoro's honor as a swordsman wouldn't allow it, and he'd rather be defeated fairly than have to resort to using venom to defeat his opponent. This is just one that Zoro would even be offended to be offered it, much less decide to eat it on his own.
2 Love: Urouge's Unnamed Devil Fruit
Urouge has a Devil Fruit that allows him to convert some of the damage he takes directly into strength. This would likely be Zoro's favorite Devil Fruit power to obtain. It's not too crazy and doesn't require him to change his fighting style at all.
All it would do is boost his already impressive strength when he inevitably gets injured during a battle. This would let Zoro keep his honor and integrity as a swordsman while still giving him a solid power boost to aid in his journey to the top.
1 Hate: Rust Rust Fruit
The Rust Rust fruit allows the user to rust anything they touch, including other people. Zoro actually lost one of his swords to this fruit, and he absolutely hates it. He wants to collect swords and doesn't seem to be one that would want any sword to be destroyed, not just legendary ones.
Zoro would refuse to ever use this ability and would likely be terrified of accidentally ruining his own weapons. This would be hands down the worst ability for Zoro to receive.