I think only the PI can list a grant as a grant obtained. If you work on the project you can list that under some kind of "relevant experience" section.
This seems a bit conservative for me.
I have a heading that reads "Grant Activity" and there are subsections for Active Grants, Completed Grants and Unfunded Grants.
Each listing is set up the same:
Role: PI Co-I Consultant* Amount: $$$$$$$ (or Unfunded)**
Funding Source: NIMH, NIDA, NICHD, Dept of Education, American Psychological Foundation etc.
Project Title: Blah Blah Blah
Funding Period:
*If I'm a Co-I or Consultant I list the PI in Parentheses after my Role
For example: Role: Co-I (PI: S. Sparks)
**If unfunded but competitive (i.e., some kind of score or percentile ranking) I list that here as well.
If you are earlier in your career, I think its acceptable to list your role as Graduate Research Assistant or Methodologist or whatever, as long as your name and title appears in the actual grant application. If your name doesn't appear in the grant I would ask your mentor for advice.
Just my thoughts.