O. Henry's short stories are one of my favourite reading material when I wish to relax and be entertained.
As in the case of other writers, some of his stories are superb, while others are mediocre.
I am giving a list of 18 short stories which are, according to me, his best ( though he has written over a hundred short stories). I am sure you will enjoyreading them, as I was :
1. Two Renegades
2. The Champion of the Weather
4. The Atavism of John Tom Little Bear
5.The Shamrock and the Palm
6. Law and Order
7. The Hiding of Black Bill
8. The Lonesome Road
9. The Ransom of Red Chief
10. The Buyer from Cactus City
11. New York by Camp Fire Light
12. Friends in San Rosario
13. The Hand that Riles the World
14. Jeff Peters as a Personal Magnet
15. The Whirligag of Life
16. A Departmental case
17. The Phonograph and the Graft
18. At Arms with Morpheus
All these stories are available online.