The same place that Americans seem to lose the second i in "aluminium". Ever notice that? It really is 'al-u-min-i-um'. Not 'A-lu-min-um'.

Well, the International Union of Pure and Applied Chemistry recognize "Aluminum" as an acceptable (though, not preferred) spelling and pronunciation. And I think there's some weird etymological reason for the 'f' being in the lieutenant pronunciation, but that one struck me as more unusual since you're adding the sound of a letter that isn't in the word rather than ignoring the sound a letter in the word makes (like "knife") which comes up more often.

Yup! It's pronounced that way in Canada too.

And here is/are the weird etymological reason(s) for it:

In English the word is pronounced /lɛf'tɛnənt/, except in American English in which it is pronounced /lu'tɛnənt/. However, the Royal Navy and other Commonwealth navies traditionally pronounced the word as /lə'tɛnənt/, though increasing usage of the first pronunciation has all but extinguished this version. The American pronunciation was originally the same as the British, but by the end of the 19th century had almost completely been replaced by the current pronunciation.

In Canada and New Zealand /lɛf'tɛnənt/ is standard for all branches of the Armed Forces and for other usages such as lieutenant governor or Quebec lieutenant. Australia follows the British system, with the Royal Australian Navy officially using the /lə'tɛnənt/ pronunciation.

The English pronunciation was prevalent during the 14th and 15th centuries with the word being variously spelled as lieftenant, lyeftenant or luftenant. It may have originated from a mistaken reading of the 'u' as a 'v' (u and v originally were written as the same letter), with v eventually assimilating in voice to /f/. Some sources state that the original French word lieu had an alternative form spelt and pronounced lieuf, and that the modern standard English form retains the former spelling 'Lieutenant' and the latter pronunciation, 'Leftenant'.

It has also been speculated that it may have come from a fanciful etymology which associated it with the verb 'to leave', as the lieutenant only took up his duties once his superior officer had 'left'.

Another theory comes from the fact that in typical propriety the person or persons standing to the rear-left of a gentleman held power and were typically those directly second to him. The person or persons standing to the rear-right were considered to have no or less standing than those to the rear-left, such as aides, bodyguards, wives, etc., often holding this position for simple facility rather than societal importance. This tradition remains in military parades, with lieutenants standing to the rear-left of the commanding officer (when facing the advance).

(Source: http://encycl.opentopia.com/term/Lieutenant)

Ahhhhhh, I see. That's cool. English has a lot of weird rules like that :x