Are there any sound effects in Esperanto? We're kind of weak in them in English, but you know, like pitter-patter, bang, tick-tock, bow-wow, baa baa, fizz, plop.

I found this:
http://eo.wikipedia.org/wiki/Onomatopeoj_en_Espera...

But any more? : D

Kara Risgrynsgroet - when you write "We're kind of weak in them in English..." do you mean that English is your first tongue?
In American we have a lot of onomatopoeia due to the all of the comics in our language. I don't know if the British use our terms. A great source for Esperanto onomatopeoj/sonvortoj is Asterik la Gaŭlo (and similar translations). but, indeed, there should be a more systematic listing of such terms. It would really enrich and embellish our language
Here are some from Asteriks: bum! Pof! aj, aj, aj, aj! Hmmm? Ŝŝ! paf! Tint! Bing - bong! Klong - kleng! Aŭ!!! Baf! Glut, glut, glut, glut glut - Ha! Haha! Hoho! Frap! Krak! Zumm - Ĥĥĥrr - Hi hi hi hi! Uf! Ha? Tatera tata! Slup! Hot!, ej, Glutglut, glutglut - Uuuf! Ho! (tio estas jam zamenhofa esprimo) Lek! Haaa... Ej, ĉu!
An example of spoken vs written Esperanto: 'stas preta la sup'?