What are the most important temples to visit during a one-day trip to Ujjain?

For a focused one-day pilgrimage, prioritise: Mahakaleshwar Jyotirlinga (including Bhasma Aarti if timed correctly), Kal Bhairav Temple, Harsiddhi Mata Temple, Chintaman Ganesh Temple, Ram Ghat for evening aarti, and Sandipani Ashram. A hired auto-rickshaw can cover all these in 8-10 hours comfortably.