unitasker

noun

1. A person who does a single thing at a time.“Even with scientific validation at his fingertips, Mr. Leleux frets that the Stanford study may have been done “by a bitter unitasker like me who wants to validate his own existence.””
2. A tool, particularly a kitchen utensil, which is useful only for performing a particular, specialized task“Bird’s beak: This style [of paring knife] has a shorter, curved blade that’s specifically designed for turning vegetables. It is really a unitasker and has no room on our knife strip at home.”