Banshee grab method
Associated movies See my banshee grab article
In this unusual method which has different versions, you get the pilot of the attacking Banshee ejected so you can fly it yourself - down to the ground or wherever. Only applies to Heroic and Legendary, as there's no Banshee otherwise. Suitable for all systems.
Full description
On Heroic and Legendary there's an enemy Banshee flying around at the bridge. By causing navigational trouble you can get the pilot ejected so you can board and fly down - or indeed fly wherever you want, which makes it rather different to all other methods. There are basically two ways of getting it, though each has variations. There's Sligfantry's 'rim method' in which the Banshee gets stuck in the bridge's left rim, and there's my 'arch method' in which the Banshee has trouble with the arch above the entry door. You'll find the details in my Banshee grab article, so I won't go into things here.
Checkpoint advice
See my Banshee grab article for advice, according to which way you want to get the Banshee.
Difficulty and system differences
The arch method is potentially quite easy once you've done some practice, and I'd be confident of getting it within a few tries. The rim method seems likely to take many tries however (based mainly on what I've heard for NTSC/PC).
There are certainly some system differences, but I don't have the full picture there. See the article.
History and links
Sligfantry was the one who realized you could grab the Banshee. He showed a method using the bridge rim, and a week later it got radically improved when he discovered a faster boarding method. Separately I came up with a method using the arch, subsequently refined it, then refined it again - a breakthrough which rocketed my success rate. See my Banshee grab article for more detail on all that.
It should be noted however that Banshee grabbing wasn't conceived of as a way of getting down off the bridge. Rather, it's a trick with wider scope, and reaching the ground below is merely one obvious application. Unlike all other methods of getting off the bridge, it gives you complete freedom of course, so there might be no need for you to head downwards.