I have a document where someone is suggesting we have a bulleted list with only one item. That sounds absurd to me. Doesn't a "list" imply more than one item?
Speaking as a programmer, no. A list can even contain no items at all.
Edit: on a more serious note, let's say I take a piece of paper and a pen, and make my grocery list. And then it just so happens that all I need is milk.
That piece of paper with a single word on it would still be my grocery list, and not my grocery word.
It may be grammatically correct, or correct in certain casual documents such as a grocery list (I am unaware of any grocery-list police), but is not a best or even good practice in more formal documents (anything involving an outline, for instance)—with one exception, discussed below.
Here's a correct example (I use numbers/letters only for ease of reference; a bulleted list follows the same logic):
Here's an example of what not to do:
a. Early Settlers
a. "No Taxation without Representation"
b. Colonial Warfare
3. Constitutional Congress
4. Civil War
a. States' Rights
The problem with the second example (where the first item has only one sub-item) is that without a second sub-item, the two levels are essentially equal. If the only thing I'm going to say about pre-Revolutionary times is to discuss the early settlers, then those terms are both referring to the same topic and I'm being redundant in the outline. Note item 3, which has no sub-items. That is the correct way to handle the case of only one item: pick one term and put it at the appropriate level of the outline.
Of course, as Roger Pate says, in a rough draft there may be an overriding reason to make a one-item list (as a visual cue to think further about the list), but this would need to be corrected if you never add to the list. This is the one exception mentioned above.
A list can have only one item, or even no items. However, you're doing more than just typing in some text into your document: you're creating something that people need to read and understand. For that purpose, it may very well be absurd to only have one item in your list; you have to judge based on the context of what you're writing and the expected audience. Conversely, you could use a single-item list as emphasis.
For example, if this bullet-point ends up displayed at the bottom of the page and the preceding text is ambiguous about how many items there may be, then it would be natural to become confused when arriving on the next page and a new paragraph.
Particularly if this is a rough draft to which you expect to later add items, then you should keep the solitary bullet-point; polish in later revisions as the content becomes more concrete.
If you look "list" up in the dictionary, it says a "considerable number or long series," so no, one item is not a series or a list. I think it is absurd to bullet one item. What ever happened to writing in paragraphs, instead of having to bullet everything? Inherent in its name, a "bullet" is supposed to be fast, so it's good for quick words or phrases, not whole sentences and paragraphs.
It seems as if people started bulleting EVERYTHING once we started using Microsoft PowerPoint and other software, which uses templates with preset bullets. That doesn't mean you have to always write in bullets; you can turn the feature off. If you truly have a list, then bullet it. If you only have one item, or you are writing in long sentences and paragraphs, don't bullet them; that's not what bullets were designed for, just like a "list" was not designed for one item. Then it's just a note.