Of all the geologic ages in the fossil record, which is your favourite? I'd have to go with the Cambrian, being the oldest Paleozoic period. The fossils of this age are also some of the most interesting due to the incredible diversity of invertebrate fossils (courtesy of the Cambrian Explosion). Many of the creatures preserved in Cambrian formations such as the Burgess Shale are critters you won't see anywhere else in the fossil record.