Welcome! There's lots of cool keycaps to be found! I want to collect one of every type of printing or manufacture. One of the main one's I'm missing is the Nylon keycaps. There's also blank polycarbonate (feng had a sale of these a long while back), but there haven't been any made in a while, so they are very uncommon.
Then there's the clickclack, brobot, gasmask, and especially girldc keycaps.