Which dialects pronounce "pen" as "pin"?

The Southern USA is one area where the pin-pen merger is common. It's not restricted to "pin" and "pen", but a lot of words that include /ɪ/ and /ɛ/ before nasals:

The pin-pen merger is a conditional merger of /ɪ/ and /ɛ/ before the nasal consonants [m], [n], and [ŋ]. The merged vowel is usually closer to [ɪ] than to [ɛ] (examples include: kin-ken, bin-ben, and him-hem). The merger is widespread in Southern American English, and is also found in many speakers in the Midland region immediately north of the South, as well as in less densely populated inland areas of the Western United States, particularly in Bakersfield, California. It is also a characteristic of African American Vernacular English.

Language Log has also discussed this, and examples where the vowels are pronounced the same and differently in a dialect with the merger may also shed some light on the phenomenon.

New Zealand English does this. Australians call it Kiwese.

There is a handy phrase book for Australians, which includes such 'jims' as

McKennock - person who fixes cars

pigs - small devices for pinning washing on clotheslines.

swab the dicks - a task for recalcitrant sailors.

[Sorry @Ham, I have the book (ISBN 1 86330 342 1) in front of me, and it says McKennock]

Some South Africans (I think those influenced by Afrikaaner accents, but by no means only Afrikaaners), seem to pronounced almost all vowels as "i", or nearly so to the point that they are indistinguishable to my English ears.

No doubt someone here can provide more detail on what is happening with that pronunciation.

Apart from New Zealanders - some of whom have accents so heavy they need to be translated - people Adelaide in Australia also have a distinctive accent similar to, but not as heavy, as the Kiwi one.