I use Shimano M324 SPD Pedals because:
* From the REI website:

The SPD pedals feature an expanded platform so you can ride in any shoes;great for people who have 1 bike they use for everything.

• SPD binding on 1 side provides the security and pedaling efficiency of a clipless pedal
• Standard pedal cage on the other side allows you to bike in non-cleated shoes
• Cleat tension adjusts so the binding releases when you want it to
• Chromoly spindle with cup and cone bearings

I wear Keen riding sandals in the summer to maintain my sandal tan and never have trouble walking around.