Character Above, Below

If you're in insert mode, and you want to insert the character above the cursor, hit ctrl-y. To insert a character below the cursor, hit ctrl-e. Alternatively, if you want to grab entire words above and below, you can use the following mappings (which use text objects).

inoremap <C-Y> <Esc>klyiWjpa
inoremap <C-E> <Esc>jlyiWkPa