>Poketch
Just a gimmick, but I fell in love with it. I surprisingly liked the useless apps like the coin toss which I just now realized could be used to decide split paths and evos among other stuff, but things like the friendship checker on-the-go was super useful as well. Also, props to GF for bringing back the Berry Searcher in ORAS.
>Menu
Basically a prototype for gen 6's, what with the menu being easily accessible and all. Was never a huge fan of the permanent running. In retrospect, certainly the most boring bottom screen.
>C-Gear
Not really useful on its own, just a bunch of connectivity features. I liked how you could turn it on and off, the skins were too nice to be covered by all those circles. I guess this could also count as a prototype for gen 6's, I mean you could battle and trade with others through this thing, even if it was limited to infrared.
>Menu/PSS/Super Training/Amie
I looooved the PSS when XY first came out. It's a shame it got overshadowed by the DexNav later. The PSS is surely one of the best features, allowing people to trade, battle, Game Sync, and all kinds of other stuff without the hassle that is the Festival Plaza (not to say that the latter is bad). Super Training isn't anything to write home about, since it's just a gimmick for evo stones and hordes are better for EV training. And there are plenty of people that liked Amie, so there's that too I guess.
>Menu/PokeNav Plus
This was really fun, and I mean REALLY fun. I loved seeing the DexNav fill with pokemon living in the area (and the gen 3 backgrounds!), I liked scanning random overworld pokemon, I liked seeing what's up on the BuzzNav, and I liked seeing all those trainers, pokemon, berries, and bases in the AreaNav. Plus it has the PSS too!
>Rotomdex
A map. But also access to the pokedex if you touch the black part! Besides that there's nothing else. I do like his comments, but then you beat the game and...
Yeah, ORAS definitely had the best bottom screen.