According to the Double-Tongued Word Wrester, the collective noun for unicyclists is a wobble. This makes sense as unicyclists do tend to wobble quite a lot, at least at first - I certainly wobble a bit when riding my unicycle. The collective noun for jugglers is a neverthriving - any ideas where this comes from? So is a group of juggling uncyclists a neverthriving wobble?!

There are many other collective nouns in English, some of which are rarely used or have been coined for fun. Most such words are for groups of animals or people. Relatively few are for inanimate objects. Some collective nouns come from the habitat of a particular creature, e.g. a cete of badgers, a nest of mice; others are based on a physical characteristics, behavioural traits or sounds made by animals, e.g. a prickle of hedgehogs, a sneak of weasals, a murmuration of starlings.

Here are a few more examples:

an aarmory or aardvarks
an absence of waiters
an army of frogs
a babel of words/languages
a business of ferrets
a clutter of cats
a chattering of choughs
a crash of rhinoceroses
a descent of woodpeckers
an embarrassment of parents
a fluther of jellyfish
a murder of crows
a parliament of owls
a shuffle of bureaucrats
a warren of wombats

Source: http://www.ojohaven.com/collectives/