FireGather v1.0.3resigned1
Looks up MTG cards by name. Free and open source under the GPLv3.
Use the addon by highlighting text and right-clicking. You will see two options: Look up the card on Gatherer, or navigate directly to the card image.
The latest version of the card is used, but if you are looking for older versions, those are found on Gatherer.
Data generated using https://mtgjson.com.