Mario Golf (N64)

Southpaw golfers
Hold down the L Button as you select your golfer, and he or she will golf left-handed.
Sorry, no funny-looking golf pants available
To change the color of your golfer's clothes, hold C-Left, C-Down, or C-Right as you select a golfer. Each C Button will yield a different color scheme.
Unlock almost everything New
On the title screen, press Down, Down, Left, Left, Left, Right, Right, Right (all on the D-Pad), then C-Down, C-Down, C-Left, C-Left, C-Left, C-Right, C-Right, C-Right. A jingle will play if you entered the code correctly. This will unlock all characters and courses, except for the Mario's Star course. You'll also have all 108 Birdie Badges, and Ring Shot mode will be complete.
Code Entry screen
At the Main Menu, highlight "Clubhouse," then press A while holding Z and R. "Code Entry" will appear on the next menu.

To enter these passwords, use the Code Entry trick above. "Ohs" and "zeros" are interchangeable.

KPXWN9N3 - Toad Highlands Tournament (Nintendo Power contest)
0EQ561G2 - 1st Camp Hyrule Cup
5VW689O6 - 2nd Camp Hyrule Cup
FJQ49LJA - NP Summer Scramble Tournament ( tournament)
6ENWCEYL - Mario Golf GBC Tournament ( tournament)
Y85YHH4M - Transfer Pak Tournament ( tournament)
4MVYR4P2 - Toad Highlands ( tournament)
9P0MWX4N - Koopa Park ( tournament)
QXK0EH6A - Shy Guy Desert ( tournament)
253GT6AH - Yoshi's Island ( tournament)
A0RMEHQJ - Boo Valley ( tournament)
JCW0T62V - Mario Star ( tournament)
W9WPLCQ9 - Dolphin Cup (Camp Hyrule 2000 Day 1)
H48LMN11 - NSIDER Cup (Camp Hyrule 2000 Day 2)
G10XPMCN - Ocarina Cup (Camp Hyrule 2000 Day 3)
6858NVW1 - Kokiri Classic (Camp Hyrule 2000 Day 4)
OH8WG0F9 - NOA Invitational Cup (Camp Hyrule 2000 Day 5)
Different intro
Turn on the game, and either watch the intro, or press Start to bypass it and go to the title screen. Wait on the title screen, and the next time the intro plays, DK will replace Yoshi in the intro. (It appears that you need to have DK unlocked for this to work.)
Unlock DK
To find Donkey Kong, complete 30 holes in Ring Shot mode.
Unlock Maple
To find Maple, collect 50 Birdie Badges in the Tournament mode.
Unlock Metal Mario
To find Metal Mario, collect all 108 Birdie Badges in the Tournament mode.
Camp Hyrule passwords sent in by DrkYdaWnKe.