Super Mario Bros. 2

SZNESXVK        Infinite lives
GZELVXSE        Infinite life meter (except if you hit a spike)
SXUASXOU        Quick pick up
AEUEKKGL        Special "squat" high jumps
PPXAOIAA        Princess has mega-float
PAXAOIAA        Princess has mega-float and lunar descent
PESEGLGA        Super moonjumps for Mario
AAEEZGPA        Mega moonjumps for Luigi
PENALLGA        Super moonjumps for Toad
PAXAPGGA        Super moonjumps for Princess
AEXALGZA        Speed up enemies
GOEANKAO + USEEEKKA          Walk backwards
XVVANSZK + XVNEXSZV          Super turbo running
AEVAVIIA + AENEEITA          Permanent turbo running
AXSETUAO + ESVAPUEV          Super fast run for Mario
AZEEGKAO + EIEEYKEV          Super fast run for Luigi
AXNAIUAO + ESNEAUEV          Fast run for Toad
AZXALKAO + EIXATKEV          Super fast run for Princess
AXNAZSAA + EVNALSEY          Super speed enemies

Note: There are two versions given for some of the following Codes. 
If one code doesn't work on your game, then try the alternate Code.
YESUAPTE / YESLPPTE        Strong Wart
IAVENYZE / IAVEUYZE        Strong Birdetta
YEVXVYLE / YEVZNYLE        Strong Hawkmouth
AAVENYZA / AAVEUYZA        Weak Birdetta
TPEPLAAX / TONENYAX        Birdetta spits eggs instead of fireballs (appears in late 
levels of the game)
YAXXIYZE	Strong Tryclyde
YAVXVGGE	Strong Fryguy
YAEXTPGE	Strong Clawgrip
PEEPUZAG + IUEPSZAA + TEEPVZPA        Start on World 2
ZEEPUZAG + IUEPSZAA + TEEPVZPA        Start on World 3
LEEPUZAG + IUEPSZAA + TEEPVZPA        Start on World 4
GEEPUZAG + IUEPSZAA + TEEPVZPA        Start on World 5
IEEPUZAG + IUEPSZAA + TEEPVZPA        Start on World 6
TEEPUZAG + IUEPSZAA + TEEPVZPA        Start on World 7