Who is the artist of the relief sculpture, The Last Judgment, In Vezelay? I can't find it anywhere.

There is no one artist.

Read widely:
http://www.google.com/search?rlz=1C1GGGE_enUS379US379&sugexp=chrome,mod=7&sourceid=chrome&ie=UTF-8&q=The+Last+Judgment%2C+In+Vezelay

is GISLEBERTUS Correct

This is the closest reference I've seen to any artist -- keeping in mind this has been built, destroyed, rebuilt, restored, etc., over a long period of time:

The west front, a combination of Romanesque, Gothic and 19th-century work, is not nearly as interesting as the treasures inside. Originally built around 1150 in the Romanesque style, it was given a Gothic central gable and south tower in the 13th century. Much of this was heavily restored in 1840 by Viollet-le-Duc, who also added a Romanesque-style tympanum of the Last Judgment to the central portal.
http://www.sacred-destinations.com/france/vezelay-church

Do you think I should go with Gislebertus or Viollet?

I don't know. Are you sure they were artists? Or were they the abbots or other Church official who commissioned the work?

Im not even, I may have to research a bit more. If i cannot find the artist what should I put on my homework? I don't think its Viollet because the sculpture he did, does not look like the one I have I think he did a remake of it.

The thing is ... in those days, they didn't keep track of any particular artists' names. The stoneworkers worked in groups, and there could have been many people who worked on that sculpture over time. In addition, does your question give a time or century or year on which to focus? Restorations and additions were common, and of course, they changed what they were restoring or adding to.

Nah my teacher told me to pick a relief sculpture and depict what story it tells you. And that was the easiest sculpture I found and understood. And i want to use this one, but I don't know the artist or date of it. I think it was made in the 19th century, is that right

I found this one site, but it was in French so when i used a translator it said: The tympanum surmounts the central portal of the facade is the Last Judgment. He was executed in 1856 by sculptor Pascal, under the direction of architect Viollet-le-Duc.

Does that mean Pascal is the artist?

That's referring to its latest restoration, and goes along with what I quoted from sacred-destinations.com above. So ... I'd go with that!