I think my friend used to say “jya buriburi(!)” when she got high

MacTuitui: wow, indeed, those are for serious aficionados… I’m wondering, though, if one couldn’t draw a separation between the ones used in everyday language and sometimes documented in dictionaries (that sounds like an onomatopeia, but aren’t really one) and the ones that seem to be only used to describe a sound (pure onomatopeia), especially in mangas and the likes. The list of the latter is nearly endless, since anybody could virtually create their own to reflect a sound.

I particularly remember happening upon a list of the most popular sounds for automatic weapons in mangas: some of these were quite hilarious (I think machine guns were something like “BU-DUM-BU-DUM”)…

Jeff, Lothe:
Indeed, bara-bara has many different meanings and uses (interestingly, my dict gives a slightly different definition for the katakana and hiragana spellings). When used to refer to objects (as in “all over the place”), or placement of people, I think it is common language. The way I’ve been hearing it with friends, though, is usually as “scattered”, but inside one’s head… As in “She’s a bit bara-bara sometimes…”
Of course, it isn’t much of a sliding, since we do it in English too… But I gather this isn’t something you’d say in a formal conversation, and some people might even fail to catch what you mean if you use it that way…

Anyway, thanks all for your contributions, keep’em coming!

How about some Kansai-ben? bochi-bochi seems pretty common. Also, the other day I learned hona-hona, which apparently is something people say when they part (with variations like like hona-sainara, too).

Great list, dr Dave, thanks for putting it together.

And for the craziest of you people, I have two books only dealing with 擬声語 and 擬態語.

One example, because I know you all love them.
You can laugh にこにこ、にやにや、くすくす or げらげら。Of course, the laugh can be ははは、ひひひ、ふふふ、へへへ or ほほほ, depending.