That's a very good question, so I've attempted to answer it.
First I found a list of all the stations in London, then I found a list of all the bus stops in London, and then I cross-referenced the two. I crossed stations off my original list if there was a bus stop with the same name as the station. That crossed off a heck of a lot of stations.
I was left with about 50 stations, which I researched more closely... the map in the Citymapper app was really useful for this. Some of the 50 stations were actually very close to a bus stop but it was called something else. Meanwhile four of the stations were served by buses on a Hail and Ride section, so there wasn't an actual bus stop. I removed all these stations from my list, and here's what's left.
See if you agree.
Tube stations that don't have a bus stop
Arsenal, Barons Court, Covent Garden, Embankment, Moor Park, Parsons Green, Roding Valley, Temple, West Harrow, Wimbledon Park Additionally: Wood Lane station doesn't have a bus stop, but several buses run past and there's a bus station nearby. Additionally: West Finchley is served by the 326 along a Hail and Ride section. Technically: Embankment and Temple do have bus stops, but are no longer served by night bus N550, which is on a four-year diversion.
DLR stations that don't have a bus stop
Abbey Road, Heron Quays, King George V, Pudding Mill Lane, Royal Albert, Royal Victoria, West India Quay Additionally: All Saints station doesn't have a bus stop, but several buses run past and there are bus stops nearby. Additionally: East India was on this list until Saturday, when the eastern end of route D3 was changed.
Overground stations that don't have a bus stop
Bethnal Green, London Fields, Rectory Road, South Acton, Walthamstow Queens Road Additionally: Hampstead Heath doesn't have a bus stop, but several buses stop very close by.
Other London rail stations that don't have a bus stop
Bellingham, Bowes Park, Crews Hill, Deptford, Drayton Park, Maze Hill, Northolt Park, North Sheen, Strawberry Hill, Sydenham Hill, Teddington Additionally: Albany Park, Drayton Green, Northumberland Park, Sudbury Hill Harrow and Waterloo East have bus stops very close by, but not named after the station. Additionally: Angel Road is supposedly served by the 192 along a Hail and Ride section. Additionally: Winchmore Hill may be served by the W9 along a Hail and Ride section. Additionally: Harringay is served by the W5 along a Hail and Ride section. Additionally: Knockholt will be joining this list in July, becoming the London station furthest from a bus stop.
Tram stops that don't have a bus stop
Avenue Road, Blackhorse Lane, Dundonald Road, George Street, Harrington Road, Lloyd Park Additionally: Wellesley Road doesn't have a bus stop, but several buses run past and there are bus stops nearby. Additionally: A recent TfL consultation aims to remove bus services from Waddon Marsh.
Dangleway terminals that don't have a bus stop
Both of them
...which is just one more reason why the cablecar isn't a very good transport link.