North: Hamningberg, Norway: 70°33'04.8"N / 70.551334 in decimal, right to the edge of the cliff. Although I have briefly touched down in a plane at Hammerfest airport (70°41'00.3"N/ 70.683404) so very slightly further north if places we have not stood on our own feet count.
South: Guayaquil, Ecuador: 2°09'58.3"S / -2.166182, barely scraped into the southern hemisphere at all!
East: Tokyo, Japan: 139°43'41.0"E / 139.728042
West: Santa Monica, USA: 118°32'45.9"W / -118.546085
I live in London, UK so my furthest both east and west are based on a starting point of 0°.