"poing" is onomatopoeia (and exactly the sort of thing you find in Don Martin cartoons - I have a cartoon called "Die Grosse Frosch-Story" (the Big Frog Story) in which that very word occurs for the operation of a frog's tongue in pursuit of a fly . . .
"shiny" - would be "klar" or "hell" or "blank" (like shoes) if simply shiny, or "strahlend" or "glänzend" if it shines like a star or a candle.
For "nifty" I turn to my faithful dictionary of German slang - we can say "toll" which literally means "crazy" but has turned into a superlative for almost anything, or "klasse" ("classy"), "super", "prima" ("first"), or (my personal favorite) "elefantös" ("elephantish")