Vangelis’ Chariots of Fire is suitably Epic for all sorts of things involving effort and triumph (especially in slow-mo :D).
Pat Benatar’s We Belong is also surprisingly Epic for Overcoming Adversity To Achieve The Glory That Is Rightfully Yours (as seen in Talledega Nights)
The Eagle’s Journey of The Sorceror was used as the theme to the Hitch-Hiker’s Guide To The Galaxy and has an awesome Epic Space-Mystic thing happening (it’s one of my favourite songs, but not on YouTube, I’m afraid).
Led Zeppelin’s Kashmir is also truly Epic and generally Made Of Awesome, too. Knights Of Cydonia by Muse is in the same category, IMHO.
The Utah Saints did the theme from Mortal Kombat which is a great Epic Song for fight scenes in which the Hero beats the stuffing out of legions of Gladiators/Ninjas/Red Shirts/Hired Goons/Generic Bad Guys, and I’ve always imagined that Hey Boy Hey Girl by the Chemical Brothers would be an excellent piece of music for a running Epic Car-Chase And Gun Battle through the streets of somewhere like Moscow or Prague or Marseille.
Thunder In My Heart (the Meck remix of the old Leo Sayer hit) is surprisingly Epic, too.
If you wanted to end the film on an uplifting (but extremely camp) note, then Go West by The Petshop Boys would be my suggestion.
And for a slice of Bollywood (and Bollywood is all about Epic), then Husan by the Bhangra Knights is a surprisingly catchy choice, too. (And you’ve gotta loved the pimped out Hindustan Motors Ambassador in the video, too. :D)
The 1812 Overture is one of the most Epic Songs Ever (well, the finale is), along with Guns 'n Roses November Rain, and, if you wanted something a bit edgier, try [*Thunderstuck/I]](http://www.youtube.com/watch?v=zvoeeq-BH4w) by AC/DC.
There are some good suggestions in this thread! 