In Common Priesthood, what will be our sacrifice? In Catholicism, we believe every baptized Christian participates in the common priesthood (Catechism of the Catholic Church 1547). A priest offers sacrifice to God. In that case what will be the sacrifice in common priesthood?
While it's true that it's the role and prerogative of the ordained priest to offer the sacrifice of Calvary on behalf of the people, the Mass is full of instances showing that it is also the people's Sacrifice (in the context of the Mass, the Sacrifice is Christ's once-for-all Sacrifice, mingled together, or rather offered together, for the greatest effect, the sacrifice(s) of believers consciously united with His): what makes the ordained priest unique is the exclusive ability to confect the Eucharist, something laity cannot ever do, in addition to his right as priest to perform the Sacraments (excepting Baptism and Matrimony, only a priest can perform the Sacraments technically speaking).

A representative example of this concept of the 'united effort' of priest as leader, and laity as united with him as their representative head, is found in the old Latin Rite (essentially Mass in the West for most people for most centuries in the history of the Western part of the Church, up to around 60 years ago and the introduction of the new Mass, with slightly different wording): "Pray, brethren, that my sacrifice and yours [ut meum ac vestrum sacrificium] may be acceptible to God the Father Almighty."

In this sense, laity, all believers, are also priests!

Except you perhaps mean outside the context of the Mass (the Sacrifice).

The priesthood of all believers refers to the fact that offering to God in sacrifice is inherently and historically a priestly act (and not only within Christianity). It is in this context that our prayers and personal penances, good works, and anything which can be "offered up" to God, essentially, is viewed as sacrifice.


  Hebrews 13:10-16 (DRB) We have an altar, whereof they have no power to eat who serve the tabernacle. 11 For the bodies of those beasts, whose blood is brought into the holies by the high priest for sin, are burned without the camp. 12 Wherefore Jesus also, that he might sanctify the people by his own blood, suffered without the gate. 13 Let us go forth therefore to him without the camp, bearing his reproach. 14 For we have not here a lasting city, but we seek one that is to come. 15 By him therefore let us offer the sacrifice of praise always to God, that is to say, the fruit of lips confessing to his name. 16 And do not forget to do good, and to impart; for by such sacrifices God's favour is obtained.