A very much not exhaustive list of known time machines
Back to the Future: DeLoeran DMC-12
The time machine is built inside the sports car which can provide the 1.21 gigawatts needed for time travel. The heart of the machine is the flux capacitor but it also needs plutonium – later replaced by a Mr Fusion unit that processes household waste and is a much safer and cheaper alternative. The traveler can set the destination on the dashboard console which also shows the present date and the last date they left from. After everything is ready, the car has to reach the speed of 88 miles per hour to reach the destination. The traveler must avoid contact with their past or future selves because it might end up in ripping the fabric of space-time and ending the universe.
Harry Potter: Time Turner
The magical time machine in the form of a necklace with an hourglass medal. It works with an Hour-Reversal charm that helps the traveler go back in time a few hours. A limit is usually set on how far back one can travel, in order to prevent unwanted events from happening. The traveler must also avoid contact with their past self in order to preserve the natural flow of events.
Dark: Wormhole
A cave wormhole connects three points in time that are 33 years away from each other. Entering the tunnel at present time, the two other exit points are 33 and 66 years into the past. It works with a wormhole that’s at the meeting point of the three tunnels and was opened by a nuclear power plant incident. A chair was also developed so that time travel is not limited to 33 year distances and uses the energy of the wormhole from the caves. Its use is usually unsuccessful as it kills the traveler in the process and only an upgraded version was able to work properly. A portable machine was also made that successfully transports travelers to any point in time by creating a small black hole around itself, with the use of nuclear energy.
Marvel: Quantum Realm
One can access the quantum realm by subatomic shrinking. It’s a reality where time and space become irrelevant. Time can flow there much slower but it’s also possible to access certain points in time and space through the quantum realm and travel there. A quantum tunnel needs to be opened, operated by someone who can „pull out” the traveler, appropriate suits that protect the body of the traveler, and Pym Particles that cause the subatomic shrinking.
Tenet: Turnstile
This device is not a time machine in the same sense as the others, as it’s literally an inversion machine. It flips the traveler’s (or any object's) particular motion in the timeline, so as one enters, they exit at the same point in time but traveling backwards, moving in reverse if it’s observed by someone from the forwards direction. Therefore it’s not possible to travel to any point in time in an instant. To go back 2 weeks, the traveler has to be inverted and spend 2 weeks living in reverse. Then, to return to forwards state, they have to use a turnstile again. The mechanisms of the machine are unknown as it was invented in the future, and sent back in time, using inversion.
