About outfits, while keeping in mind other events like this one will happen in the future, there is a handful that come to mind:
Iroha's swimsuit: Very notable one, it was a launch reward, never reran on its own again.
Kyoko's and Felicia's Halloween outfits: Only available in Karin's release event, which never got reran.
Yachiyo's and Mifuyu's school uniforms: Only available in Breakpoint/Spurred to Separation, which also never got reran, but notably these outfits do not provide new Home Screen lines, they just look different.
Mitama's winter outfit: Only available in her personal training event, likewise never got reran as training events never are reran, also does not provide new voice lines.
Ikumi's maid outfit: Only available in Wings in the Wind, never got reran, also does not provide new voice lines.
Any other outfits either get their events reran later on, or the outfits themselves are available through a different later event, as an example Winter Outfits from Valentine's events will always be available in subsequent Valentine's events, and Christmas outfits, Yukatas and Swimsuits are similarly meant to be available in subsequent Christmas/NY/Summer events, though we have not been experiencing this in NA due to the events being released so close to each other.
last edited at Jul 29, 2020 8:54PM