Grey Flannel Armor
The Leech
Watchbird
A Wind is Rising
Morning After
The Native Problem
Feeding Time
Paradise II
Double Indemnity
Holdout
Dawn Invader
The Language of Love

Original appearances from 1952 to 1957 - 8 from Galaxy, 2 from Magazine of F&SF, and 1 each from Fantasy Magazine and Time to Come. The 1960 edition marked the first time any of these appeared in a Sheckley collection. Most (but not all) can be found in various later retrospectives - which tells you this set is prime, vintage Sheckley.