There does not seem to be very many British Halfpennies that rate a "rare", and most of them are variations or errors.
British general circulation Halfpennies that have been designated as rare include -
1722 - copper - inverted "A" instead of "V"
1860 - copper - date on front
1862 - bronze - die letter to the left of the lighthouse
1883 - bronze - Victoria has a brooch or a rose at her neckline.
There are four, not two
1933
1937 [Edward VIII]
1952
1954
The rarest British Penny would be the 1954 Penny. There is one known to exist, maybe two, but there could be some doubt about the second.
Two pennys to watch from the pit, three pennys to sit, six pennys to sit, and a crown to sit. So about fifteen quid.
two pennys
The rarest moshling would be I.G.G.Y. To get him you need two purple dais and one black orchid.
"Pence" is the plural of "Penny". One Penny, Two Pence Five Pence, etc.
the two headed dragon is the rarest zany band.
The rarest and one of the prettiest flowers in the world is the Middlemist Red Middlemist Camellia. There are only two of these flowers in the world. One is in New Zealand, and the other is in Britain.
500i think anyway
mew and mew two
The two headed dragon
The pygmy hippo in the Western Cape of South Africa is the rarest living hippo. It is one of only two hippo species, the other being the more common hippopotamus, which is much larger.
The two rarest moshlings are Blingo and Lady Gogo To get Blingo You have to do a secret code and Lady Gogo You have to do a mission