As a vocalist, these are some of the hand percussion items I have used and how easy they were to use while singing.
Easy to handle, easy to use.
Egg Shaker
Easy to handle, a little more difficult to use.
Cylinder Shaker
A little more difficult to use style shaker.
Maracas
Extremely difficult to use style shaker.
Kashaka
A little more difficult to use, also a touch more fragile than you would think. Shaker style instrument.
Cabasa
Probably one of the easier ways to figure out hand drums. I had one that switched between snare and tom sounds.
Cajon
A little on the harder side, but a good place to start with hand drums.
Bongo Drums
Perhaps even a touch more difficult than the bongos.
Djembe
Easy to use.
Wood Block
Extremely easy to use, literally two wooden sticks.
Clave
I have always found these extremely hard to use properly.
Castanets
A little more difficult to use.
Triangle
One of the most essential hand percussion instruments a vocalist can have. Moderate difficulty.
Half Moon Tambourine
Standard style tambourine, nice for variance of sounds, but definitely a little more difficult to use.
Tambourine
Nice for actual hands free accents. When used alone, it is very easy. When used in conjunction with another hand drum, it is considerably more difficult.