since ZBX-4793, zabbix looks at display-hint. net-snmp also has an option to force always displaying string values as asci strings.

-Oa Display string values as ASCII strings (unless there is a DISPLAY-HINT defined for the corresponding MIB object). By default, the library attempts to determine whether the value is a printable or binary string, and displays it accordingly.
This option does not affect objects that do have a Display Hint.

it would be useful to have item-level checkbox for such an option - usecase being hp laserjet printers. for example :

$ snmpwalk ... host .1.3.6.1.2.1.43.11.1.1.6.1.1
SNMPv2-SMI::mib-2.43.11.1.1.6.1.1 = Hex-STRING: 42 6C 61 63 6B 20 43 61 72 74 72 69 64 67 65 20
48 50 20 43 45 32 36 30 41 00
$ snmpwalk-Oa ... host .1.3.6.1.2.1.43.11.1.1.6.1.1
SNMPv2-SMI::mib-2.43.11.1.1.6.1.1 = STRING: "Black Cartridge HP CE260A."