The following weapons can be seen in the film Skyline:
Terry (Donald Faison) carries a Beretta M9A1 (the newer rail-framed version of the Beretta 92FS) as his weapon. The weapon shown is actually an airsoft replica made by HFC. The HFC M190 runs on green gas, giving it a nice blowback. The shells, muzzle flash, and sound were added in post-production. It can be identified by the Elite-style slide mated to the M9A1-style frame.
Two US Marines are seen armed with Barrett M82A1 sniper rifles, with an additional rail added in front of the built-in rail, after landing on an adjacent high-rise. The additional rail was possibly added to make it resemble a M107 model.
A M141 SMAW-D can be seen being fired by a US Marine at the aliens.
Bushmaster XM15 "V-Match"
Dillon Aero Minigun
A Dillon Aero M134 Minigun is seen mounted on the Pave Hawk helicopter that approaches the building. After being snagged by the alien's tentacles, the minigun is seen firing wildly.