Kicking off the countdown of Doctor Who's most underused guest stars is Tamsin Greig who appeared in Series 1's The Long Game back in 2005. In her brief role as 'Nurse' (she didn't even get a proper name which makes the whole thing even worse) she was responsible for installing an infospike - it was basically a top of the range computer interface port - into Adam's head which would give the companion that never was access to all the information that Fourth Great and Bountiful Human Empire had collected. It was a short but sweet scene which only showcased the tip of the iceberg as far as Tamsin's talent as a comedy actress goes. If you want to see more of her, check out Black Books and Green Wing - or the most recent Episodes - to find out what she can really do.