bonus, cumshaw, dividend, donative, extra, gratuity, gravy, gravy train, lagniappe, perk, perquisite, tip

pensionbestowal, presentationbenefaction, beneficence, benevolence, bounty, charity, generosity, largesse(also largess), philanthropycontribution, donation, gift, offering, presentgrant, subsidyboon, manna, windfallfavor, freebie(or freebee), giveaway, premiumaward, prize, rewardfringe benefit, icing