Cards

D&D has an awful lot of spells and magic items, but a good character sheet should run to no more than a handful of pages (the fewer the better - a single side would be ideal). But there are various areas where more information would be useful, giving the player a handy reference to what their spells, magic items, and indeed class powers can do - ideally, this should not be the PHB, but rather an extract that shows only the specific items that are relevant to that character.

To that end, I've found spell cards in their various forms extremely useful for 5e. I haven't, as yet, found an equivalently good set of magic item cards - too many of the sets contain far too few of some very common items in favour of showing all the most obscure items in the book. And while cards for class powers do exist, these are even less useful, since so many class powers are adjusted by the character's capabilities. In many ways, the ideal would be the equivalent of the old 4e Character Builder, which generated the appropriate cards, and customised them for the individual character.

Hopefully OneD&D will include this functionality (if D&D Beyond doesn't already!). The downside of that, of course, being that it means buying in to the whole OneD&D ecosystem, which I'm less that keen to do!