One of the best and most popular script used is Vbulletin. Most of the reputable forums are powered by Vbulletin. The second recommendation I'd have is phpBB. It is absolutely free and open sourced versus Vbulletin which is licence based. I have used both and had no problems with either of them. If you can fork out some money I'd suggest going with Vbulletin.

Here is a list of the biggest internet forums http://en.wikipedia.org/wiki/List_of_Internet_forums. You can see most of them are powered by Vbulletin and the second most popular script is phpBB.

Regarding fresh look you can simply hire someone or buy a Template.