The U.S. Senate possesses the power to both impeach a government official and approve any treaties made by the executive branch, provided the motion wins a vote with a two-thirds majority. The Senate is also responsible for approving or rejecting presidential nominees for posts in the executive or judicial branches.
The Senate also has the power to conduct investigations into elements of the executive branch if so required, which serves the purpose of both keeping government powers in check while serving to help educate and inform the public.
Filibustering, while not an official power in itself, is the ability of the Senate to delay legislation from the executive branch. This process can also be used to block a piece of proposed legislation entirely. In order for this to happen however, a debate must be won by a two-thirds majority (known as cloture), in order to delay or block legislation successfully.
The Senate also has the power to both discipline and expel its members, provided that these actions are supported by a vote. Despite having this ability, only 15 members of the Senate have ever been expelled from the entire membership since 1789, and as such this is a very rare occurrence.