A multi-function writing instrument comprising: a front section having a writing point opening; at least a pair of marking tips held inside the front section, said marking tips being alternately selectable for extension through the writing point opening to a use position, one of said marking tips being a pencil lead marking tip; a rear section having an eraser opening, the rear section and the front section being rotatably connected to each other; an eraser holder movably housed in the rear section, said eraser holder being selectable for extension through the eraser opening; an eraser mounted in the eraser holder; and a means for propelling the pencil lead marking tip through the writing point opening and the eraser through the eraser opening upon rotation of the front section relative to the rear section, characterised in that the means for propelling comprises: a guide connected to the front section, the guide having a first guide end, a second guide end, a plurality of channels extending between the first guide end and the second guide end; a plurality of cam followers, each cam follower being slidably mounted in at least one of the plurality of channels, each cam follower being connected to a marking tip; a means for biasing each cam follower toward the eraser opening; an eraser follower connected to the eraser holder; a first cam rotatably connected to the guide, the first cam having a first cam path with a first cam apex for engaging the cam follower upon rotation of the first cam relative to the guide, the first cam apex biasing the cam follower toward the writing point opening, whereby the writing tip connected to the cam follower passes through the writing point opening to the use position; and a second cam rotatably connected to the guide, the second cam having a second cam path with a second cam apex for engaging the eraser follower upon rotation of the first cam relative to the guide, the second cam apex biasing the eraser follower toward the eraser opening, whereby the eraser passes through the eraser opening upon rotation of the cam relative to the guide. a front section having a writing point opening; at least a pair of marking tips held inside the front section, said marking tips being alternately selectable for extension through the writing point opening to a use position, one of said marking tips being a pencil lead marking tip; a rear section having an eraser opening, the rear section and the front section being rotatably connected to each other; an eraser holder movably housed in the rear section, said eraser holder being selectable for extension through the eraser opening; an eraser mounted in the eraser holder; and a means for propelling the pencil lead marking tip through the writing point opening and the eraser through the eraser opening upon rotation of the front section relative to the rear section, characterised in that the means for propelling comprises: a guide connected to the front section, the guide having a first guide end, a second guide end, a plurality of channels extending between the first guide end and the second guide end; a plurality of cam followers, each cam follower being slidably mounted in at least one of the plurality of channels, each cam follower being connected to a marking tip; a means for biasing each cam follower toward the eraser opening; an eraser follower connected to the eraser holder; a first cam rotatably connected to the guide, the first cam having a first cam path with a first cam apex for engaging the cam follower upon rotation of the first cam relative to the guide, the first cam apex biasing the cam follower toward the writing point opening, whereby the writing tip connected to the cam follower passes through the writing point opening to the use position; and a second cam rotatably connected to the guide, the second cam having a second cam path with a second cam apex for engaging the eraser follower upon rotation of the first cam relative to the guide, the second cam apex biasing the eraser follower toward the eraser opening, whereby the eraser passes through the eraser opening upon rotation of the cam relative to the guide. a guide connected to the front section, the guide having a first guide end, a second guide end, a plurality of channels extending between the first guide end and the second guide end; a plurality of cam followers, each cam follower being slidably mounted in at least one of the plurality of channels, each cam follower being connected to a marking tip; a means for biasing each cam follower toward the eraser opening; an eraser follower connected to the eraser holder; a first cam rotatably connected to the guide, the first cam having a first cam path with a first cam apex for engaging the cam follower upon rotation of the first cam relative to the guide, the first cam apex biasing the cam follower toward the writing point opening, whereby the writing tip connected to the cam follower passes through the writing point opening to the use position; and a second cam rotatably connected to the guide, the second cam having a second cam path with a second cam apex for engaging the eraser follower upon rotation of the first cam relative to the guide, the second cam apex biasing the eraser follower toward the eraser opening, whereby the eraser passes through the eraser opening upon rotation of the cam relative to the guide.