Metroid Prime: Hunters

These arenas are unlocked in different ways. Some are always there, while for others you need to play multiplayer games. Due to space, I have to put a few up here. You can unlock Gateway Arenas when you land on a new area in single-player. Another one is unlocked when you finish the game. There are 26 arenas in total.

Alinos Perch - open from begining
Combat Hall - open from begining
Compression Chamber - play 4 local games
Council Chamber - play 16 local games
Data Shrine - open from begining
Elder Passage - play 18 local games
Fault Line - play 22 local games
Fuel Stack - play 20 local games
Harvester - play 12 local games
Head Shot - play a four-player match
High Ground - open from begining
Ice Hive - open from begining
Incubation Vault - play 6 local games
Outer Reach - play 10 local games
Processor Core - open from begining
Sanctorus - play 2 local games
Sic Transit - open from begining
Stasis Bunker - play 40 local games OR a wifi game
Subterranean - play 8 local games
Transfer Lock - open from begining
Weapons - Complex play 14 local games

You must play 4 local games.

You must Land on a new level in single player.

To upgrade your gun, like missle or electro lob, get it twice. I think the more you get it, the more powerful it is, but I don't know. What I do know is you have to get it twice to charge.(Which you can, by the way.)

To unlock the Trailer for MPH, you need to place 5th or better in Regulator, Training and Morph Ball areas in the Single Player part of the game. When you do get 5th or better on each one, it will prompt you to view the trailer. After you view it, you can view it any other time by going to the Main Menu (where it says 'Touch Screen to Continue'), there will be a flashing dot in the lower left corner. Touch that dot and you'll be treated to the trailer anytime you'd like. Use the stylus to hit that dot, because using the Thumb Strap is kind of hard.