I notice some people are fixing multiple bad edits by using the "undo" function repeatedly. There's a much quicker way:
1. Click on the page's "history" tab.
2. Click on the date of the revision you want to return the page to (it's a link). So say we want to return "
Call of Duty 2" to Orca1 9904's last edit, we'd click "01:15, 22 June 2010."
3. This brings up the old revision of the page. Click "edit."
4. This brings up a normal edit screen with the addition of "Warning: You are editing an out-of-date revision of this page. If you save it, any changes made since this revision will be lost." Click "Save page" to return the article to that revision.
5. Rejoice.
This isn't the same as the mod rollback power (which IIRC deletes all the revisions you undo), so if someone else does this (say, to return a page to how it was originally posted) you can just revert that.