[trinhn812]

i already know  hydrogen (H2), nitrogen (N2), oxygen (O2), and the halogens: fluorine (F2), chlorine (Cl2), bromine (Br2), iodine (I2),

but is sulfur S8?

any other molecules i should know about?

[Sev]

i already know  hydrogen (H2), nitrogen (N2), oxygen (O2), and the halogens: fluorine (F2), chlorine (Cl2), bromine (Br2), iodine (I2),

All of these are homonuclear.  Don't forget about heteronuclear diatomic molecules like CO or NO.

[Yggdrasil]

Scientists have recently made a dipositronium molecule (Ps₂), which constists of two anti-matter particles (positrons) and two electron.

By no means would you be expected to know this for any high school chemistry course, but it's still pretty cool. 

Also, your list of homonuclear diatomics looks complete to me.  S₈ is a common form of sulfur but other forms can exist.  Another element which forms a small homonuclear structure is phosphorus, specifically white phosphorus (P₄).