It exist 3 various species, you may use. They may become with a powerful benefit, but also a drawback.
Humans: No benefit, no drawback. The standard character. Size can vary between small to several meters high. This is the main race that compones pirates and marines.
Fishmen: +50 Martial Art, +25 Martial Art & +25 Agility (in Water). Can fight in Water, during Sea Battles, can learn Fishmen Karate, but cannot eat any Devil Fruits. Fishmen may be a pirate.
Giants: +75 Swordsmanship or Martial Art & +75 Endurance. Food Cost is multiplied by 5. Cannot eat Devil Fruits. Yes Giants may be pirates and marines.
Footnote: Yes you may be a pirate or marine while being a fishman and giant but i highly recommend not being either side if ur a fishman or giant, this will let you rule a island and fight againts visiting pirates and marines which will result in more action for you and larger packs of the same race.