Kibosh

“KY-bosh” NOT “kuh-BOSH”

Cache

Like “cash” NOT “cachet”

Banal

“buh-NAHL” NOT “BAY-nul”

Nuptial

“nup-shul” NOT “nup-shoo-al”

Tenet

“Ten-it” NOT “ten-unt”

Triathlon

“try-ath-lon” NOT “try-ath-a-lon”

Affluent

“Aff-lu-ent” is technically correct, but “a-FLU-ent” is a validated pronunciation

Niche

Both “neesh” and “nitch” pronunciations are correct

Asterisk

“as-terk-isk” NOT “as-ter-ik”

Alumnae

“a-lum-nee” NOT “a-lum-nay”

Chimera

“kiy-Meer-a” NOT “CHIM-er-a”

Disastrous

“di-zas-tres” NOT “di-zas-ter-es”

Larvae

“lar-vee” NOT “lar-vay”

Mischevious

“MIS-che-vus” NOT “mis-CHEE-vee-us”

Sources: http://mentalfloss.com/article/64190/10-common-words-you-might-be-mispronouncing; http://www.infoplease.com/ipa/A0907075.html