2014 - Optimus Prime
2015 - Megatron
2016 - Grimlock
2017 - Soundwave

The 2018 Hallmark Transformers Christmas ornament has been revealed, and it is Starscream.
It will be released in July for US$16.
Previous ones were not released in Australia, so if you want this one you will need to find this one from an American source.