I have two favorite parts of the mass. The first is the penitential rite:
"I confess to Almighty God and to you, my brothers and sisters, that I have sinned through my own fault. In my thoughts and in my words. In what I have done and what I have failed to do. And I ask Blessed Mary, ever virgin, all the angels and saints, and you, my brothers and sisters, to pray for me to the Lord our God."
(Interestingly, we didn't say it today on this holy day of penance. Our penitential rite was the action of receiving our ashes rather than a verbal confession of sin.) I look forward to this part of the mass because it forces me to recognize my sin and guilt and openly ask for forgiveness. It isn't a condemnation for our sin but a communal plea for prayers and intercessions on behalf of all of our sins.
My second favorite part of mass is that part that almost always makes me tear up, if not openly cry. Immediately after the priest consecrates the Host and before we partake in it, we kneel and say:
"Lord, I am not worthy to receive you, but only say the word and I shall be healed."
An essential part of my faith is my desire to be worthy of the sacrifices made for me. That simple sentence is so completely loaded with emotion and penance and contrition. It completely encapsulates all of my feelings each week during mass.