100mph in my Geo Tracker, downhill in a 65mph zone.
It is a really steep hill on I-70 west on the west side of Dayton, OH.
My speedometer only goes to 85 but I had a friend pacing me in the other lane so he could tell me how fast I got to. That little four banger was screaming, I had it floored from the top of the hill but didn't hit 100 until I was almost at the bottom (over half a mile). I was already doing 80 at the top of the hill
The best was in my uncles '93 Mustang 5.0 (heavily modded for street drag, low 11 qtr mile, huge torque!), doing about 105mph in a 55mph.