Star Fox: Assault

Unlock Wolf in Multi-player

Get all the Friendship Medals (have all the team alive at the end of mission) in story mode. However, it was different for me. I started with Silver and got all the Silver badges and the Friendship Medals, then went back and got the Bronze badges and it gave me Wolf...

Unlock Xevious

Get all the Silver badges in story mode.

Unlock Game Levels in Multi-player

Complete the level in Story Mode to unlock it in Multi-Player.

Multi-player Match Unlockables

Unlocked..........Number of multi-player matches needed
Special Items On/Off option....5 matches.
Missile Launcher (steer the missile)....5 matches.
Missile Launcher Only Mode....10 matches.
Play as Peppy Hare (you know, the old guy)....15 matches.
Gatling Gun (the suped-up machine gun)....20 matches.
Crown Capture Mode (keep the crown the longest)...30 matches.
Titania Desert Map (from SF64)....40 matches.
Sure-Shot Scuffle Mode (one-shot kills)....50 matches.
Simple Map 4....60 matches.
Fireburst Canon (like a firework of bombs)....75 matches.
Booster Pack (makes you able to hover in air after jump)....90 matches.
Booster Pack Bout (no more searching for the packs)....110 matches.
Zoness Sea Base Map (another from SF64)....130 matches.
Wolfen Ship (Star Wolf's ship)....150 matches.
Predator Rockets (stay out of the air when this is active)....170 matches.
Cluster Bombs (B Bombs to the max)...200 matches.
Booster Packs and Launcher Tilt (self explanatory)....230 matches.
Simple Map 5 (the last Simple Map)....260 matches.

Unlock Demon Sniper

The Suped-up Sniper Rifle, you can get it by collecting all 50 flags in Story Mode. Kills in one hit, blows up tanks and arwings in one hit... You can find a flag list somewhere on GameFAGS...er, FAQS.