Hmm old sets from 2010 all the way to data.
I'll list what I can off the top of my head,
Green unsc troop transport,
Red unsc troop transport
Arctic qause hog
Black Guase hog
Lights and sounds spec ops Guase hog
Duel mode hog
Unsc elephant,
Unsc mammoth
Unsc falcon with landing pad
Unsc firebase
Unsc infinity armor bay X2
Unsc scourpian sting.
Multiple cyclops
Unsc longbow
Infection outpost and weapons rack
Unsc kestrel strike
Unsc grimlon
2 super detailed unsc drop pods
Hordes of troop packs and blind bags
4 battlescapes ( 2 complete)
A flood siege,
A flood invasion
A flood gate
2 flood hunters
A flood cyclops
Gen 2-5 covenant ghosts
Gen 2 and 3 covenant wraiths
Red covenant specter
Red covenant revenant
Covenant shadow
Shade turret and two old fashion unnameble heavy turrets.
One spirit dropship
4 covenant weapons packs with plasma cannon.
Hordes apon hordes of mini figure/ blind bags, traded and purchased figures gathered over the years. Cant really quess this one. So figures guess probably around 300 with mabey 200 unique figures.