Transformers, hands down. It was fun and action packed. The special effects were great, and although it wasn't one-hundred percent faithful to the source material, neither were Batman Begins or X-Men 1 and 2, and I praise those movies, so, you know, whatever. Optimus Prime and Megs were badass, Shia LaBouf did a great job, and Megan Fox might be the sexiest chick on the planet.
300 would be a close second... but that "Freedom isn't free" line still irks me. I suddenly felt like I was watching a goddamned Toby Keith video.