please suggest me some 1st person shooting

• Duke Nukem 3D: Megaton Edition
• Shadow Warrior Classic Redux
• Serious Sam Collection
• Quake Collection
• Heretic & HeXen Collection
• Condemned: Criminal Origins
• Deus Ex Collection
• DOOM Collection
• F.E.A.R. 1
• Fallout 3: Game of the Year Edition
• Half-Life 2 Collection
• Garry's Mod
• Left 4 Dead 2
• Prey
• Portal 2
• Wolfenstein Collection
• Thief Collection
• Unreal Collection
• Unreal Tournament Collection
• System Shock 2
• RAGE
• Dishonored
• Far Cry 3: Blood Dragon
• Hard Reset
• Halo Collection (once released)
• Borderlands 2

I would recommend Alliance of Valiant Arms(A.V.A),but since last year,Aeria Games bought ijji,and they have been ruining this awesome free-to-play since then.

Marathon

Stalker series, Deus Ex 1 and 3. System Shock 1 and 2. DOOM series, Fallout 3, Far Cry 3, Crysis 1 and 2, Hard Reset, Half Life 1 and 2, F.E.A.R. series (especially 1), Borderlands 2 (if you have a friend to play with), Payday, Left 4 Dead 2, Team Fortress 2, Bulletstorm, Battlefield Series, Amnesia (if you like horror without any actual shooting), Painkiller: Black, Metro 2033.

Bioshock series are great for story but not noticeable for gameplay.

Basically, RAGE. It's very underappreciated in terms of plain shooting gameplay and the engine is something to look at too.

Try Bulletstorm.

metro 2033/last light and the bioshock series both have great single player, borderlands series has great single player + co op, and battlefield 3 if you want multiplayer

Far cry 3, or any bioshock game.

Half-Life, Half-Life 2, BioShock, F.E.A.R., Halo: Combat Evolved, Serious Sam HD: The Second Encounter, Soldier of Fortune, The Darkness II, Quake II, DooM 3 BFG Edition.

Payday: The heist and Payday 2

I was getting worried no one would name Bioshock, I'm surprised didn't see more of "COD" fans (good!), Bulletstorm is cool, too bad they cancelled. Fear 1 was nice, then kinda sinked. There's a bunch of old-school FPS like doom, hexen, blood the chosen, etc
Far Cry (only played 1 and 3), Call of Juarez Gunslinger!, Sniper Elite v2 (with or without zombie nazies). That's it for now... but surely I'm forgetting about a ton of other petty nice games :)

Serious Sam !!!

Shogo: MAD

BF3, MW3, Black ops, Payday, Combat Arms

Rise of the Triad.

CoD inb4 hate ._.

Quake 3 Arena

Payday 2

FEAR-series (or at least only first game).

Try This

Sniper Ghost Warrior 2, Portal 1 and 2, Cs's all of them, Payday, Left 4 Dead 2, Call of Juarez Gunslinger and BioShock Infinite

Have you checked out any of the dozens and dozens of Source Mods?

There are a lot of them and quite a few of them are really awesome!

Pro tip: Desura makes installing Source Mods (and many, many other game mods) really easy, you should check it out if you're not used to installing game mods.

S.T.A.L.K.E.R. series, Metro 2033 / Last Night, Serious Sam, Bioshock series, Doom 3 BFG edition, etc.