Much less common are labial affricates, such as [pf] in German, and velar affricates, such as [kx] (written kg) in Setswana. Worldwide, only a few languages have affricates in these positions, even though the corresponding stop consonants are virtually universal.
Note that a fricative is a single speech segment, not a sequence of two sounds. In some languages (e.g. Polish) affricate and "stop plus fricative" clusters contrast very clearly, as in czysta 'clean (f.)' [tS...] versus trzysta 'three hundred' [t|S...] (the vertical line separates segments). In English the cluster [ts] occurs, as in bats, but it doesn't function as an affricate.
For special types of affricates, see also: clicks