It really depends on your needs, what you want your life insurance to accomplish.
The least expensive is term life, which gives a lot of coverage for a little money.
The other main option is whole life insurance, which builds up value over time. It's expensive for a small amount of coverage. Whole life insurance provides lifetime protection; whereas, term life insurance provides temporary life insurance, usually until yuo reach age 65 or 70.
The most popular type of life insurance is level term life insurance that provides rates and coverage that remain level throughout the term of your life insurance policy.
Here's how you can learn more about how term life insurance works and compare term life insurance rate quotes online.