As of right now my number one favorite piece of gear has to be the ASM hydrasynth. It continues to impress me that they were able to get such a good sounding synth for such a decent price. It was the first synth that ASM had developed and I really hope it isn't the last. They completely knocked it out of the park.
The major reason is because of how many options you have to change your basic oscillators into some really complex sounds with a ton of movement. The sonic capabilities are endless. From FM, Wavetables, Cross mod, and Sync to the tons of effects and different ways to route filters and oscillators. This synth just has something for everyone.
If I had to choose one other piece of gear it would definitely have to be either the elektron digitakt or the MPC one mainly jsut because I use a lot of samples in my work and they make working with samples super easy.
the piece of gear that I have been using the most frequently however has been the Elektron Octatrack MKII. It was a pain to get it the point where I was comfortable but now that I am I feel like I can make anything with it and it is easily the heart of the studio now.