What is the fastest acceleration in Nature? It seems that high-speed spore discharge mechanisms are winning the race. From a PLoS press release

Evolution has overcome this obstacle by producing an array of mechanisms of spore discharge whose elegance transforms a cow pie into a circus of microscopic catapults, trampolines, and squirt guns.
A new paper … solves the operation of squirt guns that fire spores over distances of more than 2 meters. The researchers used high speed cameras running at up to 250,000 frames per second to capture these blisteringly fast movements. Spores are launched at maximum speeds of 25 meters per second–impressive for a microscopic cell–corresponding to accelerations of 180,000 g. In terms of acceleration, these are the fastest flights in nature.

Max speed therefore is 90 km/h, a bit faster than what I achieved on the last weekend, yea, yea.