Alright guys, great choices! This reminds me of how many great features there've been in the past. It's been so long since I've played the some of the older games, so I had completely forgotten about a few of these!
I'd like to add two more suggestions, because these are features I really liked and I think they'd be great to have in a future game:
The Pokémon Dream Radar, and the Pokéwalker.
We'll have a poll up for these later today, here's what we have so far:
Here's a few others that were mentioned, but these have all appeared in more than one of the most recent Pokémon games and haven't been removed, so it's safe to assume that these will be regular features (unless you guys think they might not be, then let us know!)