The attributes below are a must.
- Star rating + # ratings
- Product variations, if any (typically in the form of color swatches)
List View vs Grid View
If your products are heavy on specs, you might opt for a List View instead of a Grid View, in which case you can show more attributes than those mentioned above. (see examples of this in best practice #185)
You can also show additional details on mouse hover (on desktop) – see best practice #165.