Lesser-known examples of onomatopaeia

 flomp - the sound of a cat taking up too much room on the bed. All night.

geklangbeplonkenbonk - the sound another German verb makes as it thuds its way through the memory part of the brain, crashes through the understanding bit, flounders about in the confusion and exasperation centres, and comes out at the other end.

snilp - the sound of another one of Tim's socks quietly disappearing in the night.

humber - the quietly disapproving noise of a pile of slowly accumulating unwashed clothes.

conblustergration - the silent, yet terrifyingly audible, sound of 1000 angry mainstream media blog commentators on an article about racism and celebrities.