Kamtronics KAM - $50
This is a basic mid 1980s digital interface. AFAIK it does packet, RTTY, FSK and AMTOR, which means it would be useful for 2m and HF things like APRS and maybe Winmail, etc.
"Stand your ground. Don't fire unless fired upon, but if they mean to have a war, let it begin here." -- Capt. John Parker