Tribe Swap Twist:

This is a very cool twist, everytime someone is voted out, they have to swap tribes all the time until it reaches merge.

Fake idols!
When someone finds an idol, they can place a fake idol in it's place so if someone looks in the same place, it will still be there and they think they get an idol. If the idol finder decides to make the fake idol, they can not use the idol for the next three tribal councils (including those they skin/win immunity for).

The ability to mutiny, or to steal a tribe member.

Exile island is also a fun one.

Survivor Auctions are great for several twists to be bought, such as;
-An advantage in an immunity challenge
-Making someone sit out of a challenge
-Idol clues
-Perhaps materials to make and hide a fake idol
-Voting someone off the jury if they make it to the final 2/3
-An idol that if it gets played on someone who gets 0 votes eliminates the holder
-The ability to see who people are voting for/have voted for
-A visit with the jury members
-A vote stealer
-A vote disabler
-A vote doubler
-An instant pass to go to exile (either for the buyer or to give to someone else)
-An instant pass out of tribal, you can't be voted out but you cant vote either (either for the buyer or given to someone else)

(I haven't read through the thread so idk if others have already said these, sorry in advance if they have!)

New Island Twist

During the pre-merge, one person will be sent to an island after every challenge. They will given the opportunity one advantage from 6 choices. 2 for a challenge, 2 for the tribe, and 2 for tribal council. The advantage will not be revealed to them until they pick one for themselves.

Secret Partner Twist

I know this isn't a groundbreaking twist, but it adds an extra layer of depth to the game. It would be interesting if the secret partners get their vote power doubled (so 2 votes cast) if they make it to merge together. This would work for the jury as well, if they made jury than they would cast 2 votes for the winner.

Losing Tribe Twist (Pre-Merge)

If a tribe is sent to tribal, they have to unanimously agree to save one person from being voted out at that tribal council. If they can't agree on a player to be saved, the winning tribe(s) will cast their votes for who they want to vote out of the losing tribe.

Twist:
Double Vote-Off

Basically, the Immunity challenge would occur, but the losing tribe would have to vote two people out of the game instead of only one.  (I  couldn't think of anything for this one either lol, srry in advance for it being sucky)

Tribes divided by age/gender

Every third tribal council, people vote to bring back one person who was eliminated and has not come back before from this process.

Offer a mutiny to two tribes. If enough people end up pulling a mutiny, put them in a new third tribe instead of the other one.

Everyone starts out on two tribes of ten.

Once you get to sixteen split them up into four tribes of four.
-They should be split by a vote and placed by dominant characteristic.
(Strength in Challenges, Social Skills, Strategic Prowess)
-For each category each castaway makes a list of remaining players ranking them in a list from 1-16 for each category.
After the three tribes have been chosen it will leave four people who are considered the most worthless in the game.
These four then compete in a special challenge.
In the order they finished they can choose to trade spots with someone currently on a tribe except for whoever got last place in the challenge.
The person who got last is immediately sent to exile island leaving a tribe of three behind.
The person remains on exile during the immunity challenge and returns to the losing tribe  after the challenge.

At the next challenge the "worthless" person will choose one player from each tribe to participate in a challenge (unless the "worthless" player is voted out, in which case the second worst player will choose the people to compete in the challenge. These people will then compete and the last place finisher will then become the "worthless" player. The other three will swap places with people on other tribes. This player is sent to exile until after the immunity challenge, where he will join the losing tribe.

This cycle can continue for as long as you want.
In case that was confusing here is an example.

Three New Tribes:

Strength: Alex, Barbara, Cody, Danielle

Strategy: Ethan, Felicia, Gary, Harriet

Social: Irene, Jack, Katie, Lane

Misfit Tribe: Mark, Neil, Olivia, Patty

Mark, Neil, Olivia & Patty compete in the "Worthless Player" Challenge.

Mark gets 1st
Neil gets 2nd
Olivia gets 3rd
Patty gets last

Mark switches with Cody
Neil switches with Felicia
Olivia switches with Lane

Tribes after the Challenge:

Strength: Alex, Barbara, Danielle, Mark (Switched with Cody)

Strategy: Ethan, Gary, Harriet, Neil (Switched with Felicia)

Social: Irene, Jack, Katie, Olivia (Switched with Lane)

Misfits: Cody (Switched with Mark), Felicia (Switched with Neil), Lane (Switched with Olivia)

Exile Island: Patty (Lost "Worthless Player Challenge)
-As part of the twist there could be an idol on Exile.

Immunity Challenge:

Strategy gets 1st
Social gets 2nd
Misfits get 3rd
Strength gets Last

Patty joins the Strength Tribe

The New Strength Tribe: Alex, Barbara, Danielle, Mark, Patty (Joined after tribe lost challenge)

The Strength Tribe votes off Mark at Tribal Council.

For the Next Challenge Tribes:

Strength: Alex, Barbara, Danielle, Patty

Strategy: Ethan, Gary, Harriet, Neil

Social: Irene, Jack, Katie, Olivia

Misfits: Cody, Felicia, Lane

Patty picks one person from each tribe to participate in the "Worthless Player" Challenge.
(Had Patty been voted out, then Olivia would have chosen.)

Patty's Choices:

Strength: Alex
Strategy: Ethan
Social: Katie
Misfits: Lane

Alex, Ethan, Katie, and Lane compete in the "Worthless Player" Challenge.
-You could also add some kind of reward to the challenge.

Ethan gets 1st
Alex gets 2nd
Katie gets 3rd
Lane gets last

Ethan, Alex & Katie become the new Misfit tribe allowing Cody and Felicia to switch with one person from the other three tribes and forcing them to join the Misfit Tribe.

Cody switches with Patty
Felicia switches with Irene

Tribes after the Challenge:

Strength: Barbara, Danielle, Cody (Switched with Patty)

Strategy: Gary, Harriet, Neil

Social: Jack, Olivia, Felicia (Switched with Irene)

Misfits: Alex, Ethan, Katie, Patty (Switched with Cody), Irene (Switched with Felicia)

To even out tribe numbers the Misfit Tribe then votes out one of their members publicly and they choose which tribe to join.

The Misfits vote out Ethan
Ethan joins the

The Misfits vote out Ethan
Ethan joins the Social Tribe

Tribes after Vote-Out

Strength: Barbara, Danielle, Cody (Switched with Patty)

Strategy: Gary, Harriet, Neal

Social: Jack, Olivia, Felicia (Switched with Irene), Ethan (Voted Out of Misfit Tribe)

Misfits: Alex, Katie, Patty (Switched with Cody), Irene (Switched with Felicia)

Exile Island: Lane (Lost "Worthless Player" Challenge)

Immunity Challenge:

Misfits get 1st
Strength get 2nd
Social get 3rd
Strategy get last

Lane joins the Strategy Tribe

New Strategy Tribe: Gary, Harriet, Neal, Lane (Joined after tribe lost immunity challenge)

I know its a really complex twist, but it would be really cool idea if someone could pull it off!

Twist: shifting tribes
After every vote, there will be a tribe swap. This will cause everyone to have to interact with everyone early on and create many different alliances, testing people's adaptability and leading to an interesting merge

Twist: nullifier
One or more people are assigned to be a nullifier. This means that at tribal, they do not cast a vote to evict, but rather choose who's vote they take away. If there is a tie, they can vote, and once it gets late enough in the game
If u want u can let them vote

Sometime in the merge, there will be a "challenge marathon" where there are 10 different challenges and whoever wins chooses between a secret idol to an ally, immunity to an ally, or a public idol to himself

I'm not a fan of twists I like basic.

So i'll say a totally stupid one.

The jury gets to vote to evict also.

You can either do it where each member gets a vote or the jury as a whole comes to a consensus

TWIST: there will be an MVP of the challenge (only 1, may it be on winning or losing team) and they can somehow interfere with tribal meeting.

example 1: if MVP is on losing team, they can cancel 3 people's votes.
example 2: if MVP is on winning team, they can sit in on the losing tribe's meeting.