Here is the full list of all 147 Counter-Strike: Source achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Be the last player alive in a round (with at least 5 players on your team)
Kill an enemy player who has been reduced to less than 5% health by other players
Kill an enemy while at 1 health
Win 5 Pistol Rounds
Kill the entire opposing team without any members of your team dying
Kill an enemy player that is dominating you
Dominate an enemy player
Start a round with all players on your team wearing the same uniform (at least 5 players)
Do at least 95% damage to an enemy who is then killed by a another player
Kill an enemy player in the same round as they kill a player on your friends list
Kill 25 enemies
Survive a shot to the head because you had the good sense to wear a helmet
Earn $125,000 total cash
Inflict 2,500 total points of damage to enemy players
Kill an enemy with an un-zoomed sniper rifle
Win 10 rounds
Kill an enemy player while they are reloading
Kill a zoomed-in enemy sniper with a sniper rifle of your own
Win a round in less than 30 seconds (against at least 5 enemy players)
Win a round by planting a bomb
Plant 100 bombs
Defuse 100 bombs
Kill 500 enemies
Kill 10,000 enemies
Successfully defuse a bomb with less than one second remaining
Defuse a bomb with a kit when it would have failed without one
Kill a CT while he is defusing the bomb
Win a round by defusing a bomb
Plant a bomb within 25 seconds
Win 200 rounds
Win 5000 rounds
Inflict 50,000 total points of damage to enemy players
Inflict 1,000,000 total points of damage to enemy players
Kill 5 enemy players within 15 seconds
KIll an enemy player with a gun they dropped that round
Rescue 100 hostages
Rescue 500 hostages
Rescue all hostages in a single round
Rescue all hostages within 90 seconds
Kill two enemy players with a single bullet
Earn $2,500,000 total cash
Earn $50,000,000 total cash
Kill an enemy with a grenade after you've died
Kill 200 enemy players with the Night Hawk .50c
Kill 200 enemy players with the KM Tactical .45
Kill 200 enemy players with the 9x19 Sidearm
Kill 200 enemy players with the 228 Compact
Kill 100 enemy players with the .40 Dual Elites
Kill 100 enemy players with the ES Five-Seven
Unlock all 6 Pistol kill achievements
Kill 1,000 enemy players with the Magnum Sniper Rifle
Kill 1,000 enemy players with the CV-47
Kill 1,000 enemy players with the Maverick M4A1 Carbine
Kill 500 enemy players with the Bullpup
Kill 500 enemy players with the Krieg 552
Kill 500 enemy players with the Krieg 550 Commando
Kill 500 enemy players with the IDF Defender
Kill 500 enemy players with the Clarion 5.56
Kill 1,000 enemy players with the Schmidt Scout
Kill 500 enemy players with the D3/AU-1
Unlock all 10 rifle kill achievements
Kill 1,000 enemy players with the ES C90
Kill 1,000 enemy players with the KM Sub-Machine Gun
Kill 500 enemy players with the Schmidt Machine Pistol
Kill 500 enemy players with the Ingram Mac-10
Kill 1,000 enemy players with the KM UMP45
Unlock all 5 sub-machine gun kill achievements
Kill 200 enemy players with the Leone 12 Gauge Super
Kill 200 enemy players with the Leone YG1265 Auto Shotgun
Unlock both shotgun kill achievements
Kill 500 enemy players with the HE grenade
Kill 100 enemy players with the knife
Kill 500 enemy players with the M249
Unlock every weapon kill achievement
Kill the entire enemy team (with at least 5 players) in a single round
Get kills with 5 different guns in a round
Kill an enemy player who is leading the hostages without injuring any hostages
Kill an enemy with the last bullet in your magazine (excluding sniper rifles)
Kill an enemy player who is on a killing spree
Shoot out 14 windows in a single round on cs_office
Kill 250 enemy players with headshots
Kill a total of 25 enemy players blinded by flashbangs
Kill an enemy player while you are blinded from a flashbang
Kill 100 enemy players with enemy weapons
Get a kill with every weapon
Take 80 points of damage from enemy grenades and still survive the round
Win a knife fight
Win 100 knife fights
Kill the defuser with an HE grenade
Kill a zoomed-in enemy sniper with a knife
Kill 100 zoomed-in enemy snipers
Kill 3 enemy players with a single HE grenade
Kill an enemy player with a knife during the pistol round
Win 25 Pistol Rounds
Win 250 Pistol Rounds
Kill 5 players in a C4 blast
As the last living terrorist, distract a defuser long enough for the bomb to explode
Win a round by picking up the bomb from a fallen comrade and successfully planting it
Survive damage from 5 different players within a round
Kill the entire opposing team without any members of your team taking any damage
Break 15 props in a single round
Use Dual Elites to kill an enemy player that also has Dual Elites equipped
Spray 100 decals
Do 5,000 damage with nightvision active
Kill 10 enemy players in a single round
Kill an enemy player who has just killed 10 of your teammates in a single round
Kill 5 enemy players with headshots in a single round
Win 100 rounds on the CS_Assault map
Win 100 rounds on the CS_Compound map
Win 100 rounds on the CS_Havana map
Win 100 rounds on the CS_Italy map
Win 100 rounds on the CS_Militia map
Win 100 rounds on the CS_Office map
Win 100 rounds on the DE_Aztec map
Win 100 rounds on the DE_Cbble map
Win 100 rounds on the DE_Chateau map
Win 100 rounds on the DE_Dust map
Win 100 rounds on the DE_Dust2 map
Win 100 rounds on the DE_Inferno map
Win 100 rounds on the DE_Nuke map
Win 100 rounds on the DE_Piranesi map
Win 100 rounds on the DE_Port map
Win 100 rounds on the DE_Prodigy map
Win 100 rounds on the DE_Tides map
Win 100 rounds on the DE_Train map
Kill an enemy player while you are airborne
Kill an airborne enemy
Kill an airborne enemy while you are also airborne
Win a round while making no footstep noise and killing at least one enemy
Win a round without your team killing any enemy players
Donate 100 weapons to your teammates
Win 10 rounds without dying and not spending any cash
Stop defusing to kill a terrorist and then successfully finish defusing the bomb
Kill an enemy player within 3 seconds of them recovering a dropped bomb
Dominate a total of 10 enemy players
Kill an opponent you are already dominating
Get a total of 100 kills on enemy players you are dominating
Kill a total of 20 enemy players that are dominating you
Dominate three enemy players simultaneously
Get 10 kills on enemy players you are already dominating during a single match
Kill an enemy player 4 additional times while you are dominating them
Kill two enemy players while you are blinded from a flashbang
Start a round on the same team as 4 of your friends, with all of you wearing the same outfit
Blind an enemy player who then kills a teammate
Win a match of at least 10 players where the entirety of each team is composed of a single clan.
Get two kills standing in the same spot with a zoomed sniper rifle.
Collect three gifts dropped by opponents.