Back to ritual casting:
Barbarian, Totem, 10th, commune with nature. (And speak with animals at 3rd). useful out of combat or intel gathering.
Ritual spells I have used with some frequency out of combat with my Pact of the Tome ritual spells which I have been slowly but surely collecting (we are now level 12).
Alarm, and Alarm + Magic Mouth (In tandem, great way to weak up the party if the PC on watch gets charmed or held)
Rary's Telepathic Bond: as a ritual, I enable an hour's worth of telepathic communication. We can split the party sometimes.
Skywrite: advertise for the bard's performances. Start rumors or commit simple libel/slander against various people in an area whom we dislike.
Water Breathing: nuff said.
Detect Magic and Identify: as rituals, helpful.
Leomunds Tiny Hut: as a ritual ... camping out becomes less stressful.
Other bits:
Paladin/Cleric: Ceremony: a variety of useful outcomes.
Bard: Song of rest: a little boost to short rest healing.
Wizard: Transmutation - the transmuter's stone has various features. It gave our human assassin dark vision ...at 14th level the wizard now can cast raise dead once per long rest ...