Equipments in CS will help you to survive longer and also having an advantage over the enemy. Tools like defusing kits and night vision goggles will enables you to win the game quickly and decisively.

Reducing damage  when hit by bullets. Getting blown with a shotgun at close range won't do kevlar any good as you will die permanently. Cost about $650.

Kevlar + Helmet

Protecting both chest region and head. Cost about $1000 .

Don't throw this when you are near within the blast radius or you'll get blind yourself eventually.

May kill an opponent if he is in the middle of the blast radius.

.....for making your moves. Blanketing areas so that enemies can't see you. But ah who cares? Just shoot through the smoke eh?

C4 cannot be bought coz it's for the T when playing in Defusing/Planting Bomb maps(de_xxx.bsp). Takes time to set it up so make sure ask your team mates to watch around for any incoming enemies.

CT needs this very badly if they want to defusing the bomb. It cuts half the time when defusing. VERY USEFUL!

This goggles enables you to see clearly in certain dark areas. Maps such as cs_assault or cs_747 have a lot of dark areas and you should buy the goggles. Well, it looks kinda like night vision goggles right?