I was the first person to use the E2M6 void glide in a Nightmare! episode run, and I broke the 9 second barrier on N4M9 :)
I worked really hard on those, though neither record lasted long in the end.
Oh, and N4M1-025, which I was obsessed with pushing the limit on. Wore my fingertips out til they were numb for days on several occasions chasing after it.
There are still plenty of runs left I want to achieve someday (N4M1-024!), but I just don't have the time and energy for Doom I used to have... :^)