Primates (Primates). The Eastern Lowland Gorilla (Gorilla beringei graueri), particularly the Mountain Gorilla subspecies, is the largest living primate. The maximum size of a male gorilla can be over 225 kg (500 lb) and 1.83 m (6 ft) in the wild, with much heavier weights recorded in captivity. Gigantopithecus is the largest known primate ever, probably averaged 3 m (10 ft) tall and weighing 300 to 550 kg (700 to 1,200 lb). It lived around 5 million years ago until about 100 thousand years ago in the region of India and China. Human beings (Homo sapiens) can attain massive weights measured in thousands of pounds (up to 1,600 lb), but these are cases of morbid obesity, tumor, and other medical malady, and enormous heights (up to 8 ft 11.1 in), due to the growth disorder gigantism. The tallest humans (who have reached heights of at least 7 ft 8 in even when not afflicted with gigantism) are the tallest living primates. Source: Wikipedia

Marsupials (Marsupialia). The Red Kangaroo (Macropus rufus) is the largest living marsupial. The maximum size of these lanky mammals is 100 kg (220 lb) and 1.92 m (6.3 ft) tall. Many much larger marsupials existed prehistorically, the largest of which was Diprotodon. This rhino-sized herbivore would have easily exceed 2 tonnes (4,400 lb), 3.3 m (11 ft) in length and 1.83 m (6 ft) in height. Source: Wikipedia

The largest species of arachnid is probably the Goliath birdeater However, of very comparable dimensions and possibly even greater mass, are the Chaco golden knee and the Brazilian salmon pink. Tarantulas have been recorded as reaching a leg width of 28 cm (11 in), a body length over 9 cm (3.5 in) and a body weight exceeding 85 g (3 oz), making them dinner plate-sized spiders. Source Wikipedia

The arctic Lion's mane jellyfish is the longest animal; the biggest had a bell (body), with a diameter of 7 feet 6 inches and the tentacles reached 120 feet. It was found washed up on the shore of Massachusetts Bay in 1870. From wikipedia

The giraffe has the longest neck and tail of all land mammals.