Handing out promotional bottle openers shows that your company is fun and relaxed. The best part is that promotional bottle openers stay with recipients for a very long time! For the next several outings your customers have, they'll open a cold one and think of your company.
If you work for a business that signs long-term work contracts with clients and customers, thank them at the beginning or end of the contract with a bottle opener and custom can cooler to toast to your valuable business relationship. This little extra effort will hopefully have them extending their contract with you in the future.