What links are the MOST quality? The BEST?

high pr domains with contextual links.

The hardest link to gain is usually the best link.

Exactly - the hardest to get is the best.
The natural - the best.

But generally speaking, one kind of links is going to hurt you, you should always use few types of backlinks strategies, diversity is key in SEO.

I would not see any 1 link is necessary but if for example wikipedia posted your link on their homepage i can say for certain your website would be indexed within a few hours and might even be on the first page of Google.

Natural links are the best, but that weren't the answer you was looking for was it ?

The best link you can get 'surgically' is an in content link, on a 'real' website or blog. As long as the link is on a quality site your winning.

Forget about PR and stuff like that. Just think 'real', 'natural'.

Too much of one type of link can be risky though... think natural blog comments, links from forums, press releases, directories to suppliment your nicer links and to emulate a more natural promotion.

Build one a day, and I guarantee you'll be ranking for competitive terms in around 90 days.

If you can email some trusted sites in your niche and they agree to link to you...those will be really good.

High PR and if you can go for relevant then it will well and good. Rahter then going for 100 Low websites go for 25 good PR websites. This will really help in your google SEO.

I'll take a link on Yahoo! front page

My "secret sauce" is are PR6 .gov backlinks. These are my secret links and they boost my websites like a mutha phuka!

Other than that, high PR contextual links like the one in my signature.

The most expensive links are "often" the best ones. A good way to get strong links and keep it affordable at the same time is buying a high PR expired domain. Even if you would pay something like $200,- then it's still cheap cause you can easily link to 10 of your sites from the homepage, which would come down to only $20/link. You can also use them to make your own "news" site out of them, especially when you have many sites to rank, and use them in a BMR style where you post to the homepage and where the links slowly drip off to innerpages.

Obvious there are also free ways to get real strong links:

- contacting webmasters and asking for a link
- writing awesome content and hope someone links back
- offering guest posts

As a general guideline you could say that when a link is hard to get or expensive that it's a good/strong link. But its important to have a good ratio of links with different pageranks.

I've seen a guy rank amazingly well with blog comments and xrumer links, he came up with a very good ratio of pr5,pr4,pr3,pr2,pr1,pr0,pr n/a and ranked for keywords that we can only dream of, how long it will hold is a different question though. It does show that the ratio is very important cause anyone else who would spam a million links would already be sandboxed big time.

The best links are ones contained on relevant websites of high quality that can actually drive traffic to the site you're promoting.

Why build links just for algorithmic purposes when you can kill two birds with one stone by taking a promotional approach.