Angkor Wat s for sure a must in Cambodia but there are a few more lesser known temples in Cambodia that are equally as impressive in my opinion. They are Phnom Chissor, Sambor Prei Kuk, Koh Ker and Phreah Vihear. the last one is my favorite because of its location atop a huge cliff in the Dangkrek Mountains (the border between northern Cambodia and Thailand). what's your favorite temple in Cambodia?
Banteay Srei and Preah Khan are pretty cool but Ta Prohm has to be my favorite because it's there where Tomb Raider (starring Angelina Jolene) was filmed. I was gob-smakcked when stepping inside the temple and the huge tree roots intertwined with the temple made look so cool.
Angkor Thom, Ta Phrom and Banteay Srei are all my favorite. Try to visit the National Palace Museum in Phnom Penh if you can. Avoid the Angkor National Museum in Siem Reap because it is poorly organized and hasn't got many collections.