My absolute favorite thing to do in 5e is when I can find a niche spell that's perfect for a situation the party finds itself in.
This naturally draws itself to the prepared casters and especially the deep spell list and ritual casting of the wizard, but unfortunately wizard is also a generally good class which means there's usually someone looking to use it in a party, and while doubling up can be fun sometimes I like to have other options.
I'd like to ideally make something strong without any glaring weaknesses: I don't want to minmax utility off a cliff.
My front runner has been an arcana cleric, which enables Wish eventually and adds a handful of common wizard spells to its list, but I'm not sure the other features of arcana are all that great, and not getting heavy armor makes me a little leery of closing to melee for cleric staples like Spirit Guardians.
Any other cool setups that enable a lot of flexibility and utility?