For most who wish to get me something from this list I would recommend things that I was going to buy anyway — just make sure that I don't accidentally buy it before you gift it!
Please note: if you have a business or academic relationship with me I will not accept any gifts, and will reject even gifts that would spoil if not used. Such an experience will not create pleasant emotions, so I strongly discourage gifts of any kind from those who are not family or close friends.
Interactive Features: Mark an item as purchased by clicking on it - if "Show Purchased Items" is on it will have a line through it when you mouse away. In case of a misclick, with "Show Purchased Items" on you can click any purchased item to mark it unpurchased.
Consumables generally make decent gift ideas. Some wise advice I saw suggested that if matching a budget, a quality version of something cheap is a better gift than a cheap version of something expensive.
One of the greatest of all gifts is time saved — investigating and progressing an open project for me would be wonderful. In some cases there might be a physical creation. Supporting others doing things that I endorse isn't bad either.
Things I'd probably enjoy, but don't think are worth buying at this time. Might make decent gifts as I'd then enjoy and think of you.
Prefer to own physical CDs for music, will accept Bandcamp (DRM free) if notably cheaper.
These should be quite difficult to acquire (or I would have already :/ ):
Most of the anime which I've seen I would like to own if I don't already.