IMHO, Catholics, orthodox. Jews, Lutherans, Calvinists, Unitarians largely anyway, baptists, Methodists, Copts, Adventists and many more denominations all pray to the over true (biblical) God. We have a thousand differences but we pray to the right guy. I have no problems sharing a prayer with almost any of these believers, and yes- I can then debate our differences with just as much vigor as before. Call me ecumenical if you wish, even call me mistaken. But there it is. I cannot however share a prayer session with someone who believes in a book that instructs him to kill or subjugate us. I cannot pray with someone whose “god” seeks our death and destruction. Your Holiness, please read that book before you Invite or befriend any more of its adherents. I respectfully submit that such gestures mislead the faithful into thinking that there’s no significant difference between God and Satan.
I don’t think Unitarians belong on that list.