High-Speed Class 10 16GB MicroSDHC flash memory card. Includes adaptor that also lets it be used as a full-size SD card.
Many older memory cards are only "Class 2", which was fine in older cameras if you were just taking photos at a moderate rate, or shooting low-resolution video. However, they're often not fast enough to support HD video or very fast photo shoots. If your movies jump, or recording cancels itself with no explanation, it might be because your Class 2 or Class 4 can't keep up. Class 10 is fast enough for almost all current uses, and runs as fast as you can!
(Please note; this is a Micro SD-HC (High Capacity) card, which means it will only work in cameras and devices designed to handle SD-HC cards (4GB or larger). In practice, almost all devices built in the past five or six years are okay with this).