Just off the top of my head, in no particular order... Not so sure about "small things" I suppose.
General:
- Riding in front of the monorail and getting an official "Monorail Co-pilot" card.
- The narration onboard the monorails (seems mostly broken these days).
- No bag check and metal detectors at every turn.
- Pleasure Island (for the late nighters).
- Disney Institute (never took the courses, but it was a great place to stay).
- The towel animals on the bed.
- The lobby water feature at the Poly.
Magic Kingdom:
- The old PoTC, complete with parrot and cannons outside, no Jack inside.
- Mike Fink Keelboats and Swan Boats, the river around the hub.
- Alien Encounter or better yet, Mission to Mars/Flight to the Moon.
- The waterfall spires at the entrance to Tomorrowland.
- 20,000 Leagues Under the Sea.
- Astro Orbiter (when it was styled like a Saturn V).
- The dragon topiary rising up out of the grass in the hub.
- An open and airy Adventureland (before the crazy, congested mess it is now).
- The PUSH trash can.
- The original Cosmic Ray's and dining area (no Noodle Station either).
Epcot:
- The original pavilion icons.
- Journey Into Imagination pavilion (Figment and Dreamfinder, Captain Eo and Imageworks w/rainbow tunnel).
- Horizons pavilion (and its message of "If we can dream it, we can do it.").
- World of Motion pavilion (except for the boring end showcase area).
- Universe of Energy pavilion (original version).
- Living Seas pavilion (original version).
- Calling everything a "pavilion."
- SSE and the original scenes, effects and narration.
- CommuniCore east/west with lots of actually interesting stuff (Astuter Computer Revue, etc.)
- The original reflecting pool behind SSE (now paved over and covered with a tarp).
- The omnibuses making the rounds around World Showcase (and even those weird characters).
- The general "edutainment" and futuristic vibe of Future World circa 1980s when it opened.
- The fountain in the dining area of The Land pavilion.
- Maelstrom (sorry, Frozen sucks).
- El Rio del Tiempo (no caballeros, por favor).
- The grand murals everywhere (which are slowly disappearing).
- EPCOT Center music/loops (though many are played in Electric Umbrella).
- All the various "street performers" (in Canada, England, etc.).
Disney-MGM Studios:
- When it promised (but never delivered) on being a grand, cohesive Hollywood inspired park.