Custom avatars needs to be put in the "Never gonna happen" in the OP.

A link to the OM forunms on Smogon would be nie, as there's a fair amount of people suggesting them.

Link to the /analysis within the /data

/data (nature), which can be done in #showdown but not on PS!, both /nature Adamant (This nature boosts Attack and lowers Special Attack), and /nature +SpA, -Atk (This nature is Modest.)

/report function

/invis funtcion for staff

Banning deletes messages, so that spammer's spam is gone once they're banned

Tiered randbats

More music

Tier in /data

An /afk command, so that when someone PMs a mod (say, to deal with a spammer in a modless room) an "I'm not at the computer right now" message responds, or when you click their name, it would say "akf", but like /user will say "OFFLINE"

A [spoiler] BBcode for the PS! forums, most have them, hides long lists

A "default tier" in the options, so that the default battle format isn't "Random"

A folder function in the teambuilder.

A "Sort teams" button (say, sort by format, sort by name, sort by creation time)

Make your own PS! backgrounds

(Jasmine suggested this, I just copy/pasted it) Suggestion: Moderator function. The ability to set a banword, available only to Leaders and above (or maybe even only admins). Simply for the case when we have spammers coming in with a particular word, or even a website. Alternatively the option to set a filter. Again, these would be short term fixes to protect the adorable users from the big scary internet.

A way to let PMs remain if, say, you disconnect while chatting

A "_____ is typing" message while someone is typing in battlechat and PMs

Suggested EVs on Smogon sets automatically being Smogon-recommended EVs

(Goddess Briyella suggested this one, and I didn't want to try and fail and sum this one up without missing something.) How about an expanded registry page/window when a user wins a rated battle and is allowed to register their account? I am suggesting that this expanded page/window requires the user to read and confirm that they understand the rules before being allowed to register. Also I was thinking that some of the more basic commands could be introduced here also, such as /rank, /challenge, /learn, and /data. I think it would be a great addition that would help every new user start off as a self-sufficient presence who is aware of the rules (and the consequences of breaking them) before they even enter lobby chat. While it's true that there are a good amount of regulars that are already registered here, I understand that PS is still in a beta state and I think something like this would be beneficial as the simulator becomes more increasingly popular and the amount of users continues to rise. ^_^

More avatars

A !research command could be useful, linking to the X/Y research threads, and a !rmt for linking to the Rate My Team forums

A better spam filter, or a filterbot (at the very least, something to detect a link to things like pornhub)

When a non-staff member uses a !command, make it become the /command

The thing with the glitch where if you try to switch while you're under the effects of Shadow Tag or the like, and the client doesn't let you pick a move. This essentially gives Pokemon like Magnezone two abilities, as they're scared to switch, less they lose the match by timer.

Having the news explain what the difference between OU and Pokebank OU is. (Okay, this is mine, but it's a ridiculously oft-asked question xD)

Namebans as well as IP bans, so that Cum Gulzzler 69 can't switch IPs and continue to spam. And maybe make trying to input a banned username instantly ban the current IP.

Automated battles, controlled by AI.

When you're banned, instead of it saying that you're unable to connect, have it say ""____ banned you." with a link the the discipline appeal subforums.

Lowering the "provisional" threshold as to stop alt-users from just repeatedly making alts until they hit a hot streak. The amount of people who want this is overwhelming xD

The ability to see what gender your Pokemon is on your team before you send it out, in case of things like Cute Charm.

The featured replays haven't been updated since Genesect was OU in Gen 5. I think this needs to be gotten on xD

A thing where two accounts with the same passwords can be switched between freely, without having to repeatedly input your passwords.

Have the tab notify you (like Facebook) when you're highlighted.

Pokemon Showdown Radio. I don't expect you to approve this, but hey, I'm including them all and quite capture this in the way this guy did: http://pokemonshowdown.com/forums/viewtopic.php?p=24846#p24846

Inverse and Sky battles as a format. Although personally I see it as an OM, it's an ingame battle style so I'm putting it here.

Multi-person PMs. Such as, Goddess Briyella wants to have a conversation with Novae and Stinson. They could do the multi-pm thing (maybe /pm Novae, Stinson, message).

A room for Friend Safaries/Friend codes.

Either removing Mega Forms from the teambuilder, or making it clear that it's not meant to be chosen, and that you're supposed to choose the Pokemon and give it -ite.