Timeshift had me quite excited for a while. Now technically it wasn't cancelled, but I will argue that it was since it had such a troubled history and the final game that was released with the name Timeshift was *not* the one originally shown.
Timeshift was delayed multiple times and switched publishers too. The final version of the game completely abandoned everything that came before and had only the name and dev team in common (IIRC). The original concept had some really cool ideas and uses for the PoP style time abilities. The player could pause, rewind (and I think, slo-mo) time which allowed for some creative gameplay and ingenious puzzle solving.
I wish I could find the youtube video but can't, however I do remember seeing one area for example, in which the player found himself stuck. Noticing an elevator suspended high above, he used an explosive weapon to destroy the cable keeping the elevator suspended, sending it hurtling to crash into the ground. He then ran and leapt onto the wrecked elevator and reversed time, reforming the lift beneath his feet and rising with it as it returned to it's original position with the cable restored.
The potential for the puzzle solving and combat situations which might've presented all sorts of interesting challenges was incredible. However, delay after delay after issue after issue that concept got canned and the game named Timeshift that eventually did get released was nothing like the promise. Instead it was a thoroughly forgettable, altogether shallow and unsatisfying FPS with some nonsense dictator/time travel story and a time gimmick that only meant the player was under no threat whatsoever since they could shoot/disarm everyone while time was paused. (Why would anyone waste their time disarming someone who can't shoot you, instead of just shooting them?)
Timeshift had a lot of potential, got many people excited then ended in tragedy and disappointment. Somewhat like my sex life.
