It is tempting here to just name favorite arms, but, I don't know if it helps in terms of identifying ones that sound dynamic and musical. I suspect that the terms "musical" and "dynamic" mean different things to different listeners, and any item that emphasizes an particular attribute of sound reproduction will sound good to some, terrible to others depending on taste and matching with the rest of the system.
Those arms that sound distinctly more dynamic (to me, lively sounding) can tend to sound harsh or "jangly" in some systems. I suspect that lively arms are doing less to damp vibration and it is the resonance that causes emphasis of certain frequencies that make them sound more dynamic. Is that good or bad? That really depends on the system. An example of a lively sounding arm is the Naim ARO. In a lot of systems, it sounds notably more lively than other arms and that is a good attribute for systems that sound dead and bloodless. But if you already have a lively sounding system (e.g., horn-based system), it might be too much.
