Based on the Yamcha Reborn Manga...

[Steven Bloodriver]

Which character would you like to be reincarnated as and when exactly in Dragon Ball history?

[In Brightest Day]

Finally Yamcha will be the universally loved character he always should have been in the fandom. It's about damn time.

[The_Destroyer]

I'd actually want to be Yamcha too.
Tien: I'd like a third eye but he's bald and I want hair
Krillin: no nose
Piccolo:no junk
Vegeta: Have to serve Frieza most of my life and have Widow's peak
Goku: I wouldn't be able to ride the Nimbus
Gohan: Chi-Chi
Goten: Chi-Chi
Trunks: My future self would suffer a lot so pass

Roshi would be cool though.

[Ki Breaker]

I would rather go as myself.. Being in Dragonball world I can learn ki control too! Wouldn't that be neat when I return
If not then I still choose my own body but with Gohans potential in it

[Ssenrof]

Just Dragon Ball?

Goku without a doubt. With his Sayain genes and my knowledge of the future, I would be invincible.

Counting Z,GT, Super?

Zeno and the Dragon God Zarama are obvious choices. But excluding gods - Frieza, Trunks, or Gohan would be easy wins. Goten too.

[dbgtFO]

Piccolo:no junk

You are Piccolo. You can create stuff oit of thin air. Why shouldn't you be capable of creating any size of junk you want?

Goku: I wouldn't be able to ride the Nimbus

Explain.

[TheUltimateNinja]

Goku: I wouldn't be able to ride the Nimbus

Explain.

Though you gain their body, you wouldn't gain their personality, therefore you wouldn't be pure enough to ride the Nimbus.

[Captain Strawberry]

If you're all basing it on power, Gohan has the most potential remember guys.

[ShadowBardock89]

Raditz. So much wasted potential to be utilized.

[MisteryOne]

Either Goku or Gohan. With Goku maybe I would have a harder time, but with Gohan I would definetly use all of my potential.

Hell, I would even become Goku Black. Knowing the future would make me invencible.

[dbgtFO]

Goku: I wouldn't be able to ride the Nimbus

Explain.

Though you gain their body, you wouldn't gain their personality, therefore you wouldn't be pure enough to ride the Nimbus.

Ah, of course. Thank you.

[Almighty Majin]

I would be Spike the Devilman and I would train my ass off and get my potential unlocked:

Train with Roshi before Goku's adventure starts and then win the 21st Budokai. Learn Mankoku Kyoutenshou and Mafuba.
Train with Korin after and drink the Ultra Divine Water and then win the 22nd Budokai.
Train with Kami and Popo and then win the 23rd Budokai.
Go to King Kai's planet via Baba's connections and train with King Kai. Learn the Kaioken.
Get on Kaio's good side so I can go to the Supreme Kai and train under him and use the Z-Sword. Learn Instant Movement.
Break the Z-Sword and have Old Kai unlock my potential.
Find the Super Dragon Balls and wish for immortality.
Go off and destroy Freeza, King Cold, Dabura, and Babidi. Take over as emperor of the universe and demon realm.
Fight Beerus when he wakes up and then seal him with the Mafuba.
Release him and then train with Whis. Learn god ki.

[Lord Frieza]

I have two options.

Frieza - Train his body to Golden Unbeatable Perfection and Rule the Universe.

Zamasu - Use my for knowledge to complete the zero mortals plan and create a perfect utopia.

[Doctor.]

Gohan legitimely has the perfect life post-Boo arc. So I'd probably pick him.

[SaiyamanMS]

Kid Trunks, somewhere around Battle of Gods. I'd be a half-Saiyan heir to the world's richest corporation, with Mai as a potential love interest.

[miguelnuva1]

If you have knowledge of the future I'd switch with Frizea during the saiyan saga so I could then go Goldeb when goku first goes ssj.

If its just my choice I would take Black's body right before he and Zamasu fuse.

[Akyon]

I would be Spike the Devilman and I would train my ass off and get my potential unlocked:

Train with Roshi before Goku's adventure starts and then win the 21st Budokai. Learn Mankoku Kyoutenshou and Mafuba.
Train with Korin after and drink the Ultra Divine Water and then win the 22nd Budokai.
Train with Kami and Popo and then win the 23rd Budokai.
Go to King Kai's planet via Baba's connections and train with King Kai. Learn the Kaioken.
Get on Kaio's good side so I can go to the Supreme Kai and train under him and use the Z-Sword. Learn Instant Movement.
Break the Z-Sword and have Old Kai unlock my potential.
Find the Super Dragon Balls and wish for immortality.
Go off and destroy Freeza, King Cold, Dabura, and Babidi. Take over as emperor of the universe and demon realm.
Fight Beerus when he wakes up and then seal him with the Mafuba.
Release him and then train with Whis. Learn god ki.

This is honestly my favourite answer so far. A hell of a lot of potential right here. Technically could be the the most overpowered character in the entire series.

[sintzu]

Goku, he has a pure heart, can get anyone no matter how high they are to be his friend & has unlimited power.

[dragonballhero]

Goten. He has a pretty chill life, and a hot girlfriend in Valese.

[ChronoTwigger]

The dog major.
Power, money and other people do the hard work.