Either:
1. BTC with switches made of aluminum foil disks glued to sponge backing. Probably the mushiest keyboards ever made.
2. Monterey K360. The rubber domes didn't feel bad, but for some reason the key shafts would stick, especially with the wide keys, which had no equalizer rods under them. Rocketboard gave away 250,000 of these, hoping that people would install their driver software and press the extra row of buttons that would take us to websites that paid ad revenue to Rocketboard.