Interview and funeral wear for two seasons is a big one.
Weddings I feel it doesn't hurt to have something on hand, but they tend to be very individual and have a long lead time.
Work event/professional meeting/gallery opening . . . for me I have to have some more casual and some creative clothes to mix in with my interview capsule. I go to some just because of artist friends, but many of these are work functions or networking for me.
Ethnic community event--- I work with a lot of Native American organizations, and my SO is a tribal government employee. We attend several events a year where I need a certain style of clothing. Sometimes modest and neat jeans and a button down will work, but depending on the level of participation I might need a long skirt, my mocs or cowboy boots, and a shawl.
Dancing-- I generally don't wear anything appropriate for the club, so danceable dress shoes and a breathable sparkly top. Same goes for concerts.
Something to wear to SOs work events and my own holiday parties. Ours are smart casual, but there is always the "how do you make it special/festive" thing. Occasionally he has a dress event but they are always modest and professional so I can wear my black interview skirt, shoes, and a top or button down.
Another huge one for me is trying to keep a variety of gear on hand for the invite i get to do an activity I enjoy but may not have the equipment myself for (horseback riding, kayaking, ect) and making sure I have the appropriate stuff for camping and fishing trips even if I only go a couple times a year.