Before getting into Weapons Guide player need to understand about Rarity first. Variants is a part of Weapons that let player notice what type of Variants they get when picking up their weapons wether it's from chest or floor.
There are 5 Variants in Fortnite each variants represent their own rarity of weapons.
Common Rarity is the easiest rarity that can be found in the game. Also deal less damages then any other rarity. Common Variants is helpful during early game fight. Quick to find.
Uncommon Rarity is a good rarity, deal more damages, less reload times and have more impact to enemies when engaging, but finding Uncommon Variants can be alittle bit hard.
Rare Variants is a really good middle rarity and can help in different scenario because of more damages output and less reload times. Rare rarity can be found in chest and floor loots sometimes it depend on RNG.
Epic Variants is one of the best rarity in Fortnite. More damage output then the other 3 and also reduce a huge reload times. It might be hard to find Epic Variants but it is worth to use it.
Legendary Variants is the best rarity that can be found in Fortnite. Find this rarity in air drop, chest or floor loots depend on your luck. Legendary