If you want to give your credit card some exercise, head out to Shinsegae Centum City in Haeundae. Why not take a stroll along the beaches and watch the sunset while you're here? It's also full of great shops and seafood restaurants, so you can spend the afternoon having a wander.
You can get tickets for a performance at Busan Cinema Center during your stay in Busan. Stroll along the beautiful beaches or visit the shops in this culturally rich area.