In Tier List v7 Order
CT Zero (Above every other MK I've faced so far, and I've faced too many to count.)
L_Cancel
Zinoto (Above every other Diddy I've faced so far.)
Roller,
Stewyian (Kinda by default, really.)
Ally (Above everyone else so far. I'm only very slowly learning how to beat him.)

??? (I've met several, and they vary a lot, so I need to iron this out somehow.)
Kel,
clowsui (I like fighting Marth for some reason, btw.)

??? (Not sure about this, as I was able to beat every Pikachu that I faced in tourneys so far, and this is supposed to be a terrible Fox MU.)
LOE1 (Oh mai gawd...),
Blue Rogue (Though it's been months since I last faced him.)
Salem
QD (The only one I know offline right now.)
Fizzle,
SneakyTako (Fiz Wiz got more wins off of me, but Tako's slightly more active than him now. They're the main sources of my improvement on what should already be a good MU for Fox. I only had wifi to rely on before then and that didn't work out for me well...)

??? (Pretty much matches TL's expression here. I don't know or remember. Offline TL mains, help me out!)
Kain,
Luminoth (Haven't played Seagull Joe yet, but I met him. I'm not 100%, but I'm sure he'll likely either be placed before or after Kain.)

??? (I need to remember.)
Zeton (The only other active Fox main besides myself that I was able to meet and face in person so far. I actually ended up placing higher than him at Armageddon, but that was only because we were in different seeds and mine was easier.)
Eddie G,
KassandraNova (Like with Seagull & Wolf, I haven't faced Nicole yet, either, but I also met her, too, and she'll likely be placed above the two Peaches if I do face her.)
Krystedez (At least back when he was more active.)
Mr. Eric (Completely different from the Marth guy, though now as long as I use Fox, he might never use ROB on me ever again.),
SneakyTako (Again.)
Juushichi (Though he's playing less Brawl for Project M, so besides him I need to figure this one out.)
Meek (Proved to me that Sonic is harshly-ironically one mid-tier I can't face well when he's being played at a top skill level. Either that or I don't know the Fox/Sonic MU as much as I thought I did.)
S2,
BeanBurrito
Berserker Swordsman
Tutu,
DLA
MX778/Karaoke_Man (My biggest, greatest offline rival. No really.),
Delta-cod,
Hadesblade
Smash 64 (I've faced him not too long ago.)
TheReflexWonder (Thought I'm not sure if I even faced him in a friendly yet.),
FalconFist
Drillbit Sammy (Be it in Brawl or Project M, really.)

??? (I need remember and figure it out.)
Juushichi (Again, prefers Project M nowadays.),
mars16
GenoSamus (The only Samus I know offline so far.)

???
Lordhelmet (The one time I finally met him in person, I can say him.)
SoulPech (Holy **** yes.)
Zeton (Again. When he's not Fox, he's this guy, instead.)
Fujin (I think he's the only one I've faced offline so far, but he still stands out.)
DLA (Again. If I could finally face Vermanubis in person, I'd likely add him here, too.)
---
I don't get too much character variety every month, so some characters are based on MU experiences that I had a while ago. I don't even remember if I faced some of these players yet.
Either way, most of this is subject to change.
This takes both offline friendlies AND offline tourney matches into consideration. Sometimes warming up for a real match can be just as experiencing as the real match itself.
Finally, remember that I am a
Midwestern
Fox Main, when viewing this list. It might clear some things up.