The VP rarely exercises his powers as President of the Senate, because a President pro tempore who is the constitutionally recognized officer of the Senate presides over the chamber and is elected by the Senate (and who is customarily the senator of the majority party with the longest record of continuous service).
In recent history a shift has occurred whereby presidents have relied heavily on their VP as their chief advisor (Cheaney/Bush and Gore/Clinton) with great powers flowing to them as a result. This trend began with Truman but culminated in recent history. Modern examples being Gore, as major proponent of IT leading to economic growth: as VP he oversaw the creation of a new tax on telecommunications companies that funded a federal program to install Internet connections in public classrooms, and the passage of v-chip technology that allows parents to block programming on their televisions. He is probably best known for spearheading the environmental revolution with his efforts for major environmental reforms including extending the ban on off-shore drilling.
Cheney is most certainly known as the most powerful VP in history, who under George W. Bush from 2000 to 2008, expanded the office's power even further. In some cases, he actually directed the president -- or at least led him in a favored direction. In 2001, Cheney presented a draft of an executive order that denied a trial or court martial to terror suspects, which the president signed within an hour [source: Telegraph].
While in office, Vice President Cheney created a special top secret classification for his files, Top Secret/SCI (sensitive compartmentalized information), now the highest classification of sensitive material [source: Washington Post via link below]. Cheney also argued vehemently for an expanded restoration of presidential powers, reasoning that they'd been limited by Congress in response to abuses by the Nixon administration (in which Cheney began his political career as an aide) and should be expanded in the face of the war on terror.
Tons of great information on the expanded powers of VPs are detailed in this article: http://www.anamericanvision.com/info/office_of_the_u_s_vice_president.php
And The 10 Most Important Vice Presidents of the US is interesting as it focuses exclusively on which vice-presidents were most influential in regards to the evolution of the office and not best/worst type analysis.