I wasn't aware hammer corals came in this form. I have several with the size and shape polyps but this one has much smaller polyps and the tentacles don't have the hammer shape. They're almost like mini plate corals
Here's a another photo that's a little clearer. For scale, that sexy shrimp is about 1-1.5 cm long.
After looking at a bunch of photos, it does look most like cristata. The colony is about the size of a volleyball and I had to cram it in my 20 gallon invert QT. Once I get it into the DT I should be able to get some better photos when it really opens up.