Most games have a forum section for this, but I didn't see one here. I haven't played for very long and probably these have been suggested before, so forgive me if they have.
* The merchant assistant should be able to repair you.
* Banker assistant should include guild store and bank.
* Wayshrine as purchasable home item.
* Text search in guild stores so we don't have to use a 3rd-party add-on
* Pricing data on items (how does any MMO leave this out?) - should show average price sold for: today, past week, past month, past year; and quantity for each
* Make the monster shoulder pieces tradeable with another monster shoulder piece... I get why they made them bound, but I'm tired of spending my few keys every day to try and get the one piece I need and just ending up with crap that I decon. Allow me to trade pieces with someone, and just disallow the transaction if each party doesn't have a monster set piece in the window. Alternatively, let me change the piece with a bunch of transmutation gems. Or allow me to exchange the piece + gems for another key or something.
That's all I can remember now. Add yours!