Unicode/ISO-10646 Restricted Zone

E000 - F8FF
Private use Area
F900 - FAFF
CJK Compatibility Ideographs (the duplicate hanja from KSC 5601-1987, the two duplicate Big-5 characters excluded from CNS 11643-1986, and some extra characters from corporate codesets)
FB00 - FB4F
Alphabetic Presentation Forms (added in 1.1)
FB50 - FDFF
Arabic Presentation Forms-A (added in 1.1)
FE20 - FE2F
Combining Half Marks (added in 1.1)
FE30 - FE4F
CJK Compatibility Forms (verticals and overlines)
FE50 - FE6F
Small Form Variants
FE70 - FEFE
Arabic Presentation Forms-B (re-arranged in 1.0.1)
FF00 - FFEF
Halfwidth and Fullwidth Forms (for full round-trip compatibility with existing ASCII+CJK coding schemes; extended in 1.1)
FFF0 - FFFD
Specials

There is also a special character

FEFF
ZERO WIDTH NO-BREAK SPACE (formerly BYTE ORDER MARK)

Note also

FFFD
REPLACEMENT CHARACTER

which can be used for characters not representable in Unicode/ISO-10646.


Part of Notes on CJK Character Codes and Encodings.