The trick is to append a "," (comma) to the hostname or IPv4/v6 address on the command line:

$ ansible all -i host.example.com, [the rest of the directive here…]
$ ansible all -i 10.17.234.197,  [the rest of the directive here…]

To run a playbook for just one host, make sure the hosts directive in the playbook contains all and call ansible-playbook like the above:

# Requires 'hosts: all' in your playbook
$ ansible-playbook -i host.example.com, playbook.yml

In both cases, the host parameter preceding the comma can be either a hostname or an IPv4/v6 address.

This works because if Ansible notices a comma, it thinks it is a list of hosts, but you are actually only defining one.