There isn't, and never has been, some definitive or exhaustive "Big List of Sins" that we can all look at and go, "Ah, this is a sin." There are clearly certain things that are sins that we all agree on, because such things have been clearly identified as sin by God's commandments.
The usual go-to to basic summary of God's Law is the Decalogue ("The Ten Commandments"). All of the traditional churches use the Decalogue as a helpful summary of good and bad (it's not exhaustive, but it is illustrative, and useful for catechetical purposes). Of course there is also no uniform agreement on how to number the Decalogue: The Orthodox have their numbering, Catholics, Lutherans, (and Anglicans?) use the Augustinian numbering, while other Protestants use John Calvin's numbering. However, regardless of how they're numbered, they are still grouped as ten.
Sometimes sin is explicit--"Do not murder" for example. But other times sin is more implicit, we are commanded to love our neighbor as ourselves, as such anything which is not loving can be called sinful. Not everything is necessarily sinful in all circumstances, and so situation and context is important. It's not sinful to make money through hard work in one's vocation, but if my accumulation of wealth is based upon the oppression of the poor, or directly hurts my neighbor, then it is problematic. Having isn't sinful, but if I am greedy and hoard my wealth, especially when given opportunity to help someone who is needy, then I am guilty of sin. Situationally, circumstantially, based upon nuance, and oftentimes more morally grey areas can affect what is sinful or not. But that is why we look to the Ten Commandments and to Christ's Great Commandment that we love God and love our neighbor as the fixed rule of what God desires from us.
The fixed rule we should seek to apply is what Christ Himself gave us as the Great Commandment, and we can also look to the Golden Rule which the Lord refers to as being the sum of all the Law and the Prophets. Fundamentally God's command is to love others, to do good to everyone. If our our thoughts, words, and deeds are at odds with this basic rule, then we have violated God's commandment, and thus have sinned.
Further, St. Paul goes so far as to say, "All that is not from faith is sin."
-CryptoLutheran