Counter Strike will require you to adapt your choice of equipment as you gain money by making kills and by planting or defusing bombs, depending on which team you find yourself in.
It is unlikely that you will be able to play your favourite weapon at the start of the game. You will have to begin with a weapon that isn't too expensive and which will be effective for killing your opponents.
The choice of weapon also depends on the map and your positioning on it, obviously it wouldn't be recommended to take a shotgun if you are playing mid on dust 2.
Counter Strike: Global Offensive offers the same tyes of weapons as the previous versions, it's down to you to find your favourite weapon!
My opinion:
I quickly got attached to the sniper rifle which can easily be used to kill with a single bullet. The only problem is that it doesn't necessarily suit everyone. The sniper rifle is difficult to control, you should remember that if you are moving about with this weapon then the bullet will rarely hit its target. So you have to co-ordinate you movement with your fire. I often play with the rifle when I don't have enough money to buy the sniper rifle. The rifle has 30 bullets and can be fired in several different ways.