Well, me (mzg) and my friend (Anch) are happy to introduce you some guides based on the most hard and interesting unique challenges. I reckon that most part of Borderlands 2 community have already completed this challenges, but it can be of big use for new players. Here we go.

Axton ECHO:http://www.youtube.com/watch?v=QygqHrAT_P8

Zero ECHO:http://www.youtube.com/watch?v=Dp1Sq-oER2s

Maya ECHO:http://www.youtube.com/watch?v=RgmoL62Liws

Salvador ECHO:http://www.youtube.com/watch?v=XnEEnHp6fEI

Challenges sorted by locations

Lynchwood challenges:http://www.youtube.com/watch?v=AFb5rxu8zIk

Wildlife Exploitation Preserve challenges:http://www.youtube.com/watch?v=3Z6bcThvNB4

Opportunity challenges:http://www.youtube.com/watch?v=2BhQH5sIVGc

The Highlands challenges:http://www.youtube.com/watch?v=-I13CXcKKjY

The Dust challenges:http://www.youtube.com/watch?v=VG0mSkn9pRI

Hero's Pass challenges:http://www.youtube.com/watch?v=L8YWic6AgFA

Arid Nexus - Badlands challenges:http://www.youtube.com/watch?v=lHYJhBzuKio

Caustic Caverns challenges:http://www.youtube.com/watch?v=_IPRMg85QqQ

Eridium Blight challenges:http://www.youtube.com/watch?v=R5hQK_Wt3eA

The Fridge challenges:http://www.youtube.com/watch?v=N_BewFjNJp0

Hard to complete (by my point of view) challenges

"Slab UHF" challenge:http://www.youtube.com/watch?v=VswpfmPGqRA

"Dying in the Light" challenge:http://www.youtube.com/watch?v=z_bWhmBm44A

"The Beginning of the End" challenge:http://www.youtube.com/watch?v=ZxJjpdvqoBY

"What's Yours is Mine" challenge:http://www.youtube.com/watch?v=kUuvytbhmKw

"This Ain't Me First Rodeo" challenge:http://www.youtube.com/watch?v=SpL6huZLlwI

How to get Vault Symbol in Terramorphous Peak:http://www.youtube.com/watch?v=lMS5q2peu8g

That's all. Hope you'll enjoy it

Very useful! I'll bookmark this for later. Cheers.

@Kaburorne: Do not mention it. Also, I see the error in the thread title, but I can not fix it :D

This is great, thanks!

I've done a lot of the stuff, but it's a good compilation to do a cleanup run.

Cool thanks for this. I'm a bit of a completionist at times so it would be great to get all of these challenges ticked off.

This is awesome. Thanks duder!

I would only look at a guide for Borderlands 2 after a first run. Don't get me wrong, I have looked for help...I did for Borderlands 2 once come to think! In this fashion though... I could not find my my way to the Fire Dragon, or how 'somebody' was being called. so I managed to find a pretty awkward 'Lets play' on You-tube, part 12 and recognized the badass with the dalhl's chest on his back who must be close then to the correct path...I had been through there. Stopped the let's play and found it right away. And I do consult a guide when I am absolutely stuck. Gawd help me w/Dark Souls....

But Borderlands 2 is about discovery. It blew my mind in a minor way when I seemingly by chance happened across a certain box linked to a quest...nicely done.

I'll maybe use a guide the 2nd time through, to see all the sights. I tend not to have patience for second runs though.