my unknown

[x3chibi]

We have no idea what it is because we thought it could be S. aureus or eidermis but we know it's not.

gram positive cocci
catalase positive
alpha hemolysis
facultative anaerobe
mannitol fermenter
whitish

Nothing seemed to match all of these.

[Cat]

How do you "know" that is is not S. aureus?
Your findings strongly suggest S. aureus (some stains do have whitish color).

[gakerty]

Do you have the means to test for coagulase in your lab? S. aureus will be coagulase (+), S. epidermidis and others will be coagulase (-). You may have access to TGA (Tellurite-Glycine Agar) plates, which differentiate coagulase + (black pigmented colonies) and coagulase - (grayish, or white)although it's certainly not perfect. By "whitish" in pigment, I'm assuming you have already tested on TGA, or do you mean regular nutrient agar? The latter usually doesn't tell you much.