Check out this site:
Sorting Comparisons with Animations
Short answer: Quick Sort
Longer answer:
The above site will show you the strengths and weaknesses of each algorithm with some nifty animations.
The short answer is there is no best all around sort (but you knew that since you said 80% of the time 🙂 ) but Quick Sort (or 3 Way Quick Sort) will probably be the best general algorithm you could use.
It is the algorithm used by default for Lists in .Net, so you can just call .Sort if what you have is already in a list.
There is pseudo-code on the website I pointed you to above if you want to see how to implement this.