coolest badge icon?

Transistor
http://vignette1.wikia.nocookie.net/steamtradingcards/images/6/60/Transistor_Badge_5.png/revision/latest?cb=20140522061842

Mine :)
But you can use this to search for some badges

http://www.steamcardexchange.net/index.php?badgeprices

Honestly, nobody can really know, but I currently have a level 5 badge of Chivalry, called Lord, and it looks cool.

Te one in my profile Lvl. 5 Escape Goat, "Sheep Guardian"
I like it more for the name than for the icon.

Depends what you like. I prefer mine for obvious reasons.

I like my 12 Years of Service badge xD

The cheapest one to craft.

These three look pretty cool, if you ask me:
1
2
3

The badges for this game are particularly cool.

Eversion foil badge

View attached image.

Terraria level 5 or foil badge.

if you are on foil badge (usally the same of crafting 5 regular bade or even less),

http://www.steamcardexchange.net/index.php?gamepage-appid-336380
http://www.steamcardexchange.net/index.php?gamepage-appid-318430 (last one is a littte demon)

some pencil if you like drawing http://www.steamcardexchange.net/index.php?gamepage-appid-248650

some pretty skull http://www.steamcardexchange.net/index.php?gamepage-appid-277950
http://www.steamcardexchange.net/index.php?gamepage-appid-318100

If you like borderlands, the foil badge is pretty nice http://www.steamcardexchange.net/index.php?gamepage-appid-49520

If you like chest http://www.steamcardexchange.net/index.php?gamepage-appid-359810

Best badges IMO:
http://www.steamcardexchange.net/index.php?gamepage-appid-323370

I agree there's the badge that you want and there's the one you earn. It's all about your achievements.