Here I'm going to give you 6 choices. These choices are the ones that I feel you'll use the most. Just like 1. e4 of course there are other options, but I'm keeping it simple. None of these choices is bad in my opinion. I play all of them. However, I'll give each a rating in a percentage to give you a feel about how good i think each one is/how much I like to use it. It is said that 50% of all king pawn games are sicilian though. What I'll do is when ever I give you choices they will add up to 100%, but I'll give the choices that I think are best higher ratings than the ones that I think are not so good, but still mentionable.

1. ...c6 The Caro-Kann(5%)
1. ...c5 The Sicilian (40%)
1. ...d5 The Scandinavian(15%)
1. ...e6 The French Defense(13%)
1. ...e5 (20%)
1. ...Nf6 The Alekhine Defense(7%)