Aironet Wireless, November 1999
With the company's market cap near an all-time high and rumblings of Cisco becoming the first trillion-dollar market cap company, the company ponied up a paltry $799 million to acquire Aironet Wireless for its first enterprise wireless LAN solution. The $800 million amounted to mere pocket change, but proved to be a great acquisition. At the time, wireless certainly wasn't the norm, but the shift to wireless had clearly begun.
Cisco also acquired Airspace in 2005, giving the company a controller-based solution, and, of course, complemented these solutions with the Meraki acquisition last year.