Timeshift is a unique experience, but misses the mark in alot of areas.
The director of the project, Doctor Aiden Krone, takes the Alpha Suit and travels into the past. Once there he alters history, naming himself ruler of the Krone Magistrate that controls a dystopic world.
The protagonist, a fellow scientist whose name is never spoken, nor does he ever speak,(Gordon Freeman clone?) then takes the Beta Suit and follows Dr. Krone back to the year 1939 (in an alternate timestream) to a place called Alpha District. He then proceeds to assist the Occupant Rebellion against Dr. Krone.
Thorughout the game, you will acquire quite an impressive arsenal of over 12 diffrent unique weapons such as the Hell-Fire, which is an SMG equiped with a flame thrower, that's bullets are ignited once fired, and the EMF cannon, which is a very destructive plasma type rifle. Another useful tool is the Clutch Grenade, which is very similiar to Halo's Plasma grenade. All of the weapons in Timeshift are unique looking, handle well, and are always fun to fire. I couldnt wait to unlock the next gun, just to see see how unique it might be.
The Timeshift powers are obviously the real draw, and allow you to slow, stop, and reverse time during firefights to give you innumerable advantages. For instance, you can pause time, run up to the leader of the group of your enemies, steal his weapon, and shoot a crowd of enemies in the face, then drop a Clutch grenade on them. Un-pause and watch all of the gory destruction take place. On the negative side, these powers could have been used to make amazing puzzle segments, but instead had the standard, "pull a switch and run for the door before it closes" puzzles. Very dissapointing.
The enemies have fairly standard AI that will flank and throw grenades from time to time, but for the most part its nothing to special. You will encounter other time bending units who put up some stiff opposition, requiring you to use your own time powers in order to defeat them.
The physics engine seems to be the same one used in Half-Life 2, but its not put to anywhere near as good of use, though watching your enemies gibs rain down in slow motion never gets old. There are certain "WTF?!" moments in which bodies will fly incredible distances, but usually it stays within the realm of possibility. Certain areas in the environments are semi-destructible, making for some interesting firefights during a couple of missions that take place in an apartment building, but after that, you probably wont even notice the chunks flying from random pillars.
Timeshift definately has its quirks, including some silly overly repetitive dialogue, not much mission variety, very boring stretches, and an abrupt ending, but the creative weapons and enviroments, fun to use time powers, and great effects seem to balance it out.
Overall, its a decent game that shouldn't be missed, but it shouldnt be first on the list either.