That depends largely on where you want to go. Downtown Thunder Bay, about 4 miles from Thunder Bay, ON Airport (YQT-Thunder Bay Intl.), can be a bit tricky to drive in. Make things easier by renting something compact, fuel-efficient, and a cinch to handle. That said, Thunder Bay is a handy base from which to explore many of the bays in Ontario. If your journey is more about cruising down highways, then you may like something with more trunk space and room to move. How about a full-size car or a standard SUV?