A good one for start-ups in Palo Alto, Mountain View, or parts of SF like Potrero Hill is a Parking Ticket perk.
I used to allow each employee to expense 2 work-related parking tickets a month.
This is extremely high ROI. It lets you not worry about circling for parking too much, moving your car too often, being late for a meeting, etc. Only once you have “two strikes” do you have to worry too much about parking regulations.
Cheap perk with high ROI — makes time much more efficient where employees are moving cars in areas that are parking challenged.