blatant, flagrant
blatant means obvious
flagrant means obvious and offensive

boom, boon
boom means a period of rapid growth
boon means is a turn of fortune

come, go
come is used for movement toward the speaker
go is used for movements away from the speaker

biannually means occuring twice a year

bimonthly means occuring twice a month (or once every two months)

biweekly means occuring once every two weeks

semiannually means occuring twice a year

semimonthly means occurring twice a month

semiweekly means occurring twice a week

or just avoid these and use twice a year, twice a month, etc.

for a litle more confusion, biennially means occuring once every two years

adverse, averse
adverse means unfavorable (she had an adverse reaction to the drug)
averse means opposed to (he was averse to going into deep water)

anxious, eager
anxious means worried (he was anxious about the surgery)
eager means enthusiastic desire (she was eager to start college)

assure, ensure, insure
assure means to put at ease (he was able to assure them of success)
ensure means to guarantee (the lab results could ensure the purity of the milk)
insure means cover with insurance (they can insure your loss)