FDC3-6DA4 10 green jemeralds for an extra life
9DC3-6DA4 50 green jemeralds for an extra life 
DDC3-6F04 Each green jemerald gives you a life
5D66-DFA7 Slower timer
F366-DFA7 Faster timer
6DCB-A404 + 6DCC-A4D4 Die when touched (regardless of jemeralds)
DD6B-DF07 Infinite time
D46B-DF07 Time goes by 2x as fast
D06B-DF07 Time goes by 4x as fast
D7C2-6704 Each green jemerald is worth 3
DBC2-6704 Each green jemerald is worth 9
FBC2-6704 Each green jemerald is worth 19
49C2-6704 Each green jemerald is worth 25 (extra life on each one)
DDCA-AD04 + DDBB-6D61 Infinite lives
DF83-D765 Start with 1 life instead of 5
D783-D765 Start with 3 lives
DB83-D765 Start with 9 lives
FB83-D765 Start with 19 lives
9D83-D765 Start with 50 lives
BB83-D765 Start with 99 lives
1DCC-A4D4 Walk through enemies if you have no red jemeralds 
D4CB-A7D4 Don't lose all red jemeralds when you get hit
C2BB-6FA1 Don't lose green jemeralds when you fall and die
8BAB-6DD9 No enemies or jemeralds--good for exploring, switch off effects
to advance
FFCB-A7D4 Red jemeralds set to 10 after you get hit--must have at least 1