Abilities
All abilities are learned through experience and leveled up through use - I'm so tired of leveling up only to automatically pull the new fireball spell out of a magic hat, it's old. Spell progression is unique and fun. If I've got to be high enough level and have enough friends to enter a dungeon to seek out a rare fireball scroll that is protected by an elite world mob that not many other players have learned yet, it makes your character feel more personal, same with the renown suggestion above.
Lifesteal - for casters and melee, please! I just love this type of spell.
Enchanting weapons and custom armor/stat enhancements - allow players to use a crafting system in order to make custom stat enhancements for their gear, allow us to create the recipes.
Fast travel - Please, the only type of fast travel we need in the game should be spells that can summon or teleport you to certain places, and these spells are only acquired by certain classes, and are very hard to come across. Other than that we should utilize things like carriages, boats, and dare I say it? On foot... These are the best ways to make friends.
Resurrection - Please, please, I don't want another game where every single character can randomly pop by a downed character and revive them. Please restrict this to healing specialty classes only.
Please keep the trinity - enough said.