The grace of our Lord Jesus Christ be with you all. Amen.
The MT text has with all of the saints. The Greek witnesses present seven different endings (not counting those that append Amen).1
A benediction of this type is quite unusual at the conclusion of an apocalyptic writing, but it is quite fitting for this one which incorporates epistolary features for the churches and is to be read in them (Rev. Rev. 1:3-4+).2
1 Bruce M. Metzger, A Textual Commentary on the Greek New Testament (Stuttgart, Germany: Deutsche Bibelgesellschaft, 1994), Rev. 22:21.
2 Robert L. Thomas, Revelation 8-22 (Chicago, IL: Moody Press, 1995), Rev. 22:21.