I was just thinking of making this thread. Guess you beat me to it
Anyways, I agree, tmnt has had so many iconic soundtracks over the years there's alot to choose from. Me personally, my all time favourite tmnt soundtrack is the battle theme from the Original Cartoon when the turtles are ready to kick ass. Listening to it sends chills down my spine and I was very happy when Nick used it again for their crossover episode.
Other tmnt soundtracks I love are:
1. Foot Clan and Shredder theme from the 2k3 series.
2. The theme of splinters origin from the original 1990 film.
3. Battle theme from the red sky section of the OT which replaced the traditional battle theme.
4. OT Technodrome theme
5. Music used for slow and emotional scenes in the Nick series (I can't remember the exact name of the track, but I remember it playing during "The Wrath of Tiger Claw" when Karai finds out Splinter is her father and in "Transdimensional Turtles" when the turtles enter the lair)
6. Happy ending music from the 2k3 series
7. Splinters theme from the 80s series, which has different variations. For e.g. Splinter offering wisdom or telling a backstory from Japan.
8. The big apple theme from Turtles in Time, as well as a few other tracks from that game.
9. Channel six music.
10. Go Ninja Go