Halo Interactive DDB
Founded in 1996, straight out of high school.
The first digital media agency in Estonia. Sold to DDB Worldwide in 1997. Folded in 2001 along with dotcom bubble.
A Northern Star of its time, Halo spawned a few dozen influential early internet people (UX, design, web development, software engineering) who have had notable influence on the Estonian and European startup scene over the decade since.
For some serious nostalgic flashbacks, see snapshots of halo.ee in 2001 on WayBackMachine: