Landsknecht, pl. Landsknechte: German soldiers fighting in the Swiss way with pikes (best weapon against armoured cavalry). Their troupe was founded by Emperor Maximilian I. (1459 - 1519). The Swiss soldiers didn't like this because they lost chances of empoyment in Germany. There are some old folk songs about the heartfelt enmity between both.
We can't speak of mercenaries here; since there were no standing armies in this time the soldiers were hired at the beginning of a war and fired at the end.
Later on the lansquenets partly took up firearms; the pikes grew obsolete in the 30 years war. Grimmelshausen, participant in this war, mocked "the poor guys meandering aimlessly over the battlefield with their heavy pikes".
With the beginning of standing armies in Germany the lansquenets disappeared in history.
First German regiment of a standing army was the Hessian Life Guard Regiment (1621 - 1920) in Darmstadt.