Is it legit to sell your Uplay/Steam account?

local laws > valve TOS

Legal? That all depends on where you live and the laws there.

Against ToS? Definitely. Most companies put a clause in their Terms of Service for anything that has an account that you cannot buy, sell, trade, or giveaway accounts. There's actually a very good reason for this. The reason is that if you buy an account from someone, the original owner may change their mind about it and then claim the account was stolen. The company is almost always going to side with the original owner because there is going to be evidence of them creating the account. That clause in the ToS is specifically to protect the company in case that does indeed happen.

And if you think that would never happen, it does happen. I've been on the end of having to hear from the person who bought the account after the original owner reported the account stolen. Never a fun situation for a support rep to be in because they violated the terms and there's no way in hell they are getting the account back and that person may well be out a good amount of money now as well. It can happen, and it can happen even if you are given the account by a close friend or even a family member. People can be assholes.

So put simply, don't do it. You may change your mind down the road and then that puts people in a shitty situation.

Meh its not really illegal, but it breaks ToS... so be careful

its really easy to get scammed and i wouldnt recommend trading accounts unless you absolutely have to. Be sure you find a good middleman and a really reliable person because the original owner may at any time decide they want the account back and recover.

Technically no but people do it anyway see

Aside from breaching the Terms & Conditions, it's not difficult for the original owner to reclaim to the account they sold, claiming their account has been stolen, and whoever they traded with is left with nothing.

Not illegal, but not smart either.

No - It's against TOS, and for good reasons... selling it is at very high risk of the buyer as well as the seller. Expect scams, claim backs, hacked/stolen accounts or getting the account banned, etc.

Selling it to a friend should be okay I guess :p

But you can sell a pen and gift the account with it xD

Q. Is it legit to sell your Steam?
Ans. According to the ToS, No.

I have no idea about Uplay since i don't use Uplay.