Still widely available is Colmán Ó Raghallaigh’s An Táin, the ground-breaking Irish language graphic novel or Úrscéal Grafacha illustrated by Barry Reynolds. A superb visualisation of the ancient Irish epic it is highly recommended and for those who are learning Irish there is an excellent online English language translation provided by the publisher Cló Mhaigh Eo.
For another take on the Táin Bó Chuaille (in the English language) try the webcomic of Irish writer and artist Paddy Brown with his The Cattle Raid of Cooley.
A very different take is the French-based Cú Chulainn, a manga style of illustration producing some visually arresting images (just don’t expect too much historical accuracy). Several other related titles are also published by the very interesting (and multi-lingual) Oghme comics collective and are well worth visiting.