Influential

adjective

1. having or exerting influence, especially great influence :  

three influential educators.

noun

2. a person who exerts or can exert strong influence :

according to influentials of the fashion industry.

Examples from the web for influential

Perhaps as online education continues to grow, such extension programs will become more powerful and influential.

The decision gives corporate lobbyists, already much too influential in our political system, an immensely powerful weapon.

The problematic data appear in two papers about ways to manipulate human cells that were published in highly influential journals.