Feel free to write why, or If you know write what do you like most on tracks.
Please also post how long you played the game, so I know eg. if it was 1 day or 3 months.
You can browse all tracks online here: http://stuntrally.github.com/tracks/index.html
For me it will be: Test1-Flat and TestC8-Align

Okay kidding, played first too much while developing.
Hah, this will be difficult, so I'll make a probably too long, grouped list:
From long, rally tracks: A3-Canyon, J13-Tropic/J17-JungleCanyons, F12-HighPeaks, V2-Volcanic, G2-Coast/G5-Climb
From stunt tracks: S14-Refinery, S12-Infinity (or simply the most difficult tracks)
From the short fast curly tracks: J3-Rocky, T3-Orange, C2-CanyonRun/C1-Hairpins, F7-blur3, I8-Pharaoh, D1-simple
Since I'm also a "mud and water fan": I10-Treasure, J18-Tiny, J16-MudMad, J11-Temple
From the weird tracks: X1-Magic, V1-Dark, F13-Castle, D12-Sandstorm, R1-Mars
My favourite scenery would be Autumn.
If I could pick just 1 now, it would be S7-HighMadness, IDK, it's just like from a fairytale.