What is the geometrical structure of OF₂?
Oxygen difluoride ($\ce{OF2}$) is analogous to water ($\ce{OH2}$) both in terms of structure and hybridization. 



$\ce{OF2}$ has 4 ligands around the central oxygen, 2 $\ce{O-F}$ bonds and 2 lone pairs.  Just like in water these 4 ligands assume a roughly tetrahedral geometry around the central oxygen. Again like in water, the $\ce{F-O-F}$ angle is less than the perfect tetrahedral angle (109.5°), in this case being around 103°.

Carbon disulphide ($\ce{CS2}$) is linear.  It is analogous to the 3 carbons in allene, in both compounds the central carbon is $\ce{sp}$ hybridized making the $\ce{X=C=X}$ structure linear.