In that sort of far-but-near future setting, like Minority Report, where we have some amazing technology like awesome computers and cars that drive themselves, but life really isn't that different, there's a mad scientist who mucks about with time travel. You, as a Time Agent or maybe just the Special Division of the FBI, whatever, have to travel through time, and stop his creations. Also, while a badass, you don't have the typical tough guy macho attitude, but are more suave. I'm thinking you're kinda like George Clooney in Ocean's 11, only with rocket launchers and lasers. Also, there will be a gun that shoots other guns, as in you can plant a gun like a turret in a far wall. The turrets will have different types, flame throwers, lasers, shoots chainsaws, depending on what you want it to do.
Along the way, you fight ninjas, dinosaurs, zombies, robots, ninja-robot cyborgs, zombie-ninjas, dinosaur-robot cyborgs (all combinations of those four things, including a zombie-dinosaur-ninja-cyborg). Gameplay would be mostly cover-based shooter, with a "linear" story. I say that, because there will be time-travel involved, it'll just be linear relative to the player. Cool bits will involve early in the game, coming across a field of dead dinosaurs, only to later in the game mow down the dinosaurs when you travel back to that time to protect yourself. Also missions where you are watching yourself run and fight through areas with a sniper rifle picking off threats that were unknown to you the first time through. Lots of cool reveals will be done using the travel back in time to see what happened in the moments before you arrived the first time, etc.
The final level will be a big boss fight on a space station where you defeat the boss by crashing the station into a volcano. It ends with you riding a motorcycle through the rapidly disintegrating hull and jumping over the volcano and into the future, which is the time where the game began.
I think I'll call it TimeSpark. And it'll have like 6 awesome taglines. Ranging from "Make Einstein your *****" to "When Time Flees, Gun It Down."
The sequel, TimeSpark 2: Tempus Tempest involves you gaining mental control over time and how those weird gargoyle monsters from that episode of Doctor Who where Rose saved her father and therefore made a rift in time try to kill you.