Halo Campaign Evolved has 9 new weapons from other games in the franchise according to the its description on Steam. Place your bets, ladies and gentlemen.
>Energy Sword (Confirmed)
>Battle Rifle (Confirmed)
>Needle Rifle (Confirmed)
>Fuel Rod Gun (Highly likely, was partly in the original game, reworked and introduced as a usable weapon in Custom Edition)
>Flamethrower (somewhat likely, cut weapon from the original game, was reintroduced with Custom Edition)
>Sentinel Beam (somewhat likely, enemy weapon, introduced in later games)
>SMG (somewhat unlikely, would serve as a replacement for the classic CE AR)
>Beam Rifle (unlikely, it's a well known and infamous weapon)
>Gravity Hammer (very unlikely, because 343i seems to like that weapon for some reason)