The item that does not belong in the group is la pasta dental (toothpaste).
Here's the reasoning:
- The other items (los patines - skates, la pelota - ball, el palo de golf - golf club) are all sports or physical activity-related equipment.
- "La pasta dental" is not related to sports; it is a personal hygiene product used for dental care.
Thus, it doesn't fit with the theme of sports or physical activities.