Here is MY Top 5 'train fights' in TFI (and an apt acknowledgement for the title VEERAM) :
Number 5
Endhiran
A hi-tech technology based stunt sequence which was freshly introduced to TFI. It has both physical and technology driven stunts in equal measures making it quite exciting during every single watch.
http://www.youtube.com/watch?v=9IZs6RvCGQw
Number 4
Captain Prabakharan
The uncrowned emperor of TFI strikes back with what he is best at. It not only show cases the physical strains, but also specific skills and challenges. A pure joy to watch the sequence unfold.
www.youtube.com/watch?v=69o0uzJdsA4
Number 3
Thiruda Thiruda
A quite intelligently executed stunt sequence, capturing the whole sequential journey of a train, which not only stresses the performers but the Camera man too. A 'trip-to-the-edge-of-the-seat' ARR music and MR's immense idea to hold all your attention, are at plenty.
http://www.youtube.com/watch?v=Ja6lNcnFwH4
Number 2
Murattukalai
And that's the mother of All stunts. This sequence is a School for train stunts. The physical strain, the co-ordination and the timing, the main factors of a stunt performer, are sky high here.
http://www.youtube.com/watch?v=ImK0G7QeBYg
Number 1
Senthoorapoove
Brilliant or much more if there is a higher word. Its not only my favorite train fight, it has all the awesome actors and actress making the whole stunt sequence just awesome. Right from Chandrasekar shouting - Sentil Waving - Ramki/Nirosha Running, its a pure mastery of execution (and of coarse if you have watched the whole movie, you will at least cry out once - COME ON before the end). Then, the best part arrives with an EPIC BGM - VK along with Azhagu - watch these 2 stunt magicians perform some nail biting acrobatics. Film Students come back, please.
http://www.youtube.com/watch?v=rmNB8OryAOU
Number X
Veeram
Pure power on display. 'Hair-thin-second' miss, "Thala" gone. Watch it to know what I mean, as at this point I cannot tell you more. This sequence will not only sweep you of your feet but will leave you wanting more.
Happy that my list is gearing up as TOP 10. Way to go TFI. Hats of to Siva, Silva, Vetri and all performers notably Ajith who was ready to take the hit or the fall.
[Extra : Care to note the jump from the train to the platform @ the station, a gigantic slo-mo]