Depending on where you live and climatic suitability, I'd suggest Ilex crenata 'Sky Pencil', Ilex crenata 'Mariesii' Azara microphylla or Euonymus japonicus 'Green Spire'. Of these, the Sky Pencil is the most distinctly columnar, followed closely by the euonymus. The 'Mariesii' is very slow growing but in time can reach a significant height. All, being broadleafed evergreen shrubs, are quite tolerant of pruning should it be necessary.

Nandina domestica is also very tolerant of shade and tends to grow taller than wide so can be used in this situation but is considered invasive in some parts of the country. Irish yews are also very columnar when young (they fatten up as they mature) and are the most shade tolerant of conifers.