Can you tell us some of them?
Maybe, if a lot of us have same, then start a thread on fixing?
Sure. Hundreds was hyperbole but here are a few. If I spent more time I could probably remember more. I don't know how difficult any of these would actually be to implement but:
1) Reduce Jack of Trades recharge time to 23 hours so that the time doesn't move forward as long as a player does it within the hour.
2) Make Citadel resource caps automatic, calculated based on what is building, with the option to add an additional amount. (No reason for players to calculate this by hand..)
3) Make ore/charcoal goals automatically reduce as ore and charcoal is spent.
4) Allow the game server messages to show up even when the filter for "Game" is set (possibly with a setting in options to disable them)
5) Make the message for special attack power show up when the game is set to filter.
6) Make spec restore potions trigger the messages for 50%/100% restored.
7) Fix the amulet of fury on female characters so that it doesn't float away from the character like it does now.
8) Change D&D timers for Tears of Guthix, Manage Thy Kingdom, to be reset at GMT game time, (on penguins day if it is weekly) so that players aren't punished for not being able to play at a set time.
9) Make the morytania elite legs bonus for renewals either work a) anywhere, or b) when the legs aren't equipped.
10) Show highscore tracking data on the official runescape adventures log similar to how fansites manage this.
11) Return F2P to the shortened highscores table so that fansites can capture that data.
12) Allow players to select colors for outfits using the new clan cape color diagram. Allow them to select primary and secondary, or type in #HEX values so that they can ensure matches.
13) Update the houses so that the bedroom outfit change stations are the current equivalents instead of the outdated versions from six years ago.
14) Allow shops to sell items in notes, possibly for a surcharge. Currently several shops have daily stock of certain items but players have to buy them in sets of 28 and bank. Let the shop sell us notes.
15) Add sandstone and the troll minigame to the RS gamebar.
I have more somewhere, but its hard to remember them all.