Just when you thought one stylus for the 3DS would be enough. You were wrong.
"Touch! Double Pen Sports" is an upcoming sports game for the 3DS that uses, wait for it, two touch pens. The game features seven different sports, such as baseball and boxing, and three different types of "exercise" games.
These exercise games focus on using both the right and the left hand at the same time and are divided in to three categories: "Separate", "Trace" and "Symmetry". But the real story here is two touch pens!
While this is the first 3DS game to feature two touch pens, Namco Bandai did release Taiko no Tatsujin games for the Nintendo DS that used two touch pens, too. And the original Nintendo DS (the fat one), had a nub on the strap that could conceivably be used as a second stylus. But those were 2D.
『タッチ！ ダブルペンスポーツ』2本のタッチペンで遊ぶ新感覚スポーツゲーム [ファミ通.com]