Two that I am particularly proud of:
3 x mile with 400m jog recovery (run in two minutes).
4:24, 4:23, 4:20
A solo 16k (ten miles in my head) on the track in 50:35, the last 8k being covered in 24:55.
Unfortunately I think both of those workouts I may have left a bit too much on the track.
In my first year out of college, ran 4 x 1 mile with one of my teammates who was still in college. We had a decent amount of rest, around 5-6 minutes. The goal was to run one 1/4 of each mile at around 60 seconds and the other three at even pace, with the first mile having the first 1/4 the 60 second one, the second mile having the second 1/4 at 60 and so on. (i.e. 1st mile was run around 60, 68, 68, 68, the second mile was run around 68, 60, 68, 68, the third mile was around 68, 68, 60, 68 and the last one around 68, 68, 68, 60). We averaged right around 4:24, which is my fastest mile repeat workout ever and it was made tougher by the uneven splits with the 60 second 1/4 being thrown in.
I race much better than my workouts. That being said, I did 16x400 at 67-68 before running 3:42