The spinning top from the movie Inception, modeled by comparing scenes from the movie.
It is an inch tall (2.5 cm) and about the same width; it may seem a bit small at first but after playing with it for a while I find it very comfortable. Mine was printed in stainless steel and it will spin for over a minute; the puckered texture gives it a nice feel and somehow the outer curves are very smooth.
One word of advice: tempting as it may be, try not to spin it on a nice wooden surface, it may scratch it and in some cases dig itself a comfortable dent to rest on (see picture). Then again, sometimes you want an excuse to buy a new desk :)