The best- It was the first time that I was travelling in AC and my first AC journey was in TVC Raj 2 tier AC ( A1-25,27,29,30). I was just 11 yrs at that time. I was amazed by the service and food.
The worst- Two yrs earlier, I planned to go to TCR with my mother and brother in Hapa Tirunelveli SF in 3AC. When reaching Verna, a place in northern Goa, we came to know that a goods ahead had derailed and all the ACs were switched off. We struggled in that B1 compartment without AC for a frustrating 12 hrs!!!!!, that too in an atmosphere like the Sahara desert!!!!!!!!!!!