Warren buffet: A good business that can be purchased for less than the discounted value of its future earnings.blog

George Soros: An investment that can be purchased (or sold) prior to a reflexive shift in market psychology/fundamentals that will change its perceived value substantially.

Benjamin Graham: A company that can be purchased for substantially less than its intrinsic value.

Some other examples are:

The Corporate Raider: Companies whose parts are worth more than the whole.

The Technical Analyst:  An investment where technical indicators have identified a change in the price trend.

The Real Estate Fixer – Upper: Run down properties that can be sold for much more than the investment required purchasing and renovating them.

The Arbitrageur: An asset that can be bought low in one market and sold simultaneously in another at a higher price.

The Crisis investor: Assets that can be bought at fire sale prices after some panic has hammered a market down.