A pump, comprising: an outlet port; an outlet section in fluid communication with the outlet port; an inlet port; an inlet section in fluid communication with the inlet port; a substantially hollow middle section extending between and in fluid communication with the inlet and outlet sections; a piston configured for rectilinear displacement, the piston comprising spaced-apart opposing first and second ends (92, 94), wherein the first end of the piston is operatively coupled with a prime mover; a substantially hollow ball guide configured for rectilinear displacement within the pump, the ball guide comprising: a ball disposed therewithin; and spaced-apart opposing first and second ends (42, 44), wherein the first end of the ball guide is operatively coupled to the second end of the piston; and the second end of the ball guide comprises: an opening; and one or more seals along an outer perimeter of the second end, the one or more seals configured for providing a sliding-sealing interface along the outer perimeter of the second end of the ball guide; and a seat disposed at the second end of the ball guide, characterized in that the ball guide further comprises: a plurality of spaced-apart posts extending between the first and second ends (42, 44) of the ball guide, wherein the posts are spaced apart from each other such that the ball cannot move unassisted from the interior of the ball guide but can be moved into or out of the ball guide by an operator through an opening between two of the posts. an outlet port; an outlet section in fluid communication with the outlet port; an inlet port; an inlet section in fluid communication with the inlet port; a substantially hollow middle section extending between and in fluid communication with the inlet and outlet sections; a piston configured for rectilinear displacement, the piston comprising spaced-apart opposing first and second ends (92, 94), wherein the first end of the piston is operatively coupled with a prime mover; a substantially hollow ball guide configured for rectilinear displacement within the pump, the ball guide comprising: a ball disposed therewithin; and spaced-apart opposing first and second ends (42, 44), wherein the first end of the ball guide is operatively coupled to the second end of the piston; and the second end of the ball guide comprises: an opening; and one or more seals along an outer perimeter of the second end, the one or more seals configured for providing a sliding-sealing interface along the outer perimeter of the second end of the ball guide; and an opening; and one or more seals along an outer perimeter of the second end, the one or more seals configured for providing a sliding-sealing interface along the outer perimeter of the second end of the ball guide; and a seat disposed at the second end of the ball guide, characterized in that the ball guide further comprises: a plurality of spaced-apart posts extending between the first and second ends (42, 44) of the ball guide, wherein the posts are spaced apart from each other such that the ball cannot move unassisted from the interior of the ball guide but can be moved into or out of the ball guide by an operator through an opening between two of the posts.