a nobody
a nothing
breath
breath of air
capful of wind
cipher
common man
dummy
figurehead
flatus
insignificancy
jackstraw
lightweight
little fellow
little guy
man of straw
mediocrity
nebbish
nobody
nobody one knows
nonentity
nothing
nullity
obscurity
pip-squeak
puff
puff of air
puff of wind
punk
runt
scrub
shrimp
small fry
small potato
small potatoes
squirt
squit
stir of air
waft
whiff
whippersnapper
zero
zilch