How to group by DESC order

Question

I have the following table called questions:

ID | asker 
1  | Bob
2  | Bob
3  | Marley

I want to select each asker only once and if there are

Answer 1

To get every column:

SELECT * FROM questions
WHERE id IN 
(SELECT max(id) as id, asker
FROM questions 
GROUP by asker 
ORDER by id DESC)

Improved version of the answer of @bluefeet.