This page lists all Easter eggs in Hitman: Codename 47.
Traditions of the Trade
Terminator's Box of Roses
In Traditions of the Trade, there is a box of roses in the Florist's shop. It can be obtained by getting Frantz Fuchs' room key, and retrieving the florist's letter from the reception. Delivering the letter to the florist will trick him to giving Agent 47 a box of roses, containing a Shotgun.
This is a reference to "Terminator 2: Judgement Day" where the Terminator retrieves a lever-action shotgun from a box of roses.
In Traditions of the Trade, the peace summit being held is called "U.N.F.C.K."