opportunist

from WordNet (r) 3.0 (2006)

opportunist
    adj 1: taking immediate advantage, often unethically, of any
           circumstance of possible benefit [syn: {opportunist},
           {opportunistic}, {timeserving}]
    n 1: a person who places expediency above principle [syn:
         {opportunist}, {self-seeker}]

from The Collaborative International Dictionary of English v.0.48

Opportunist \Op`por*tun"ist\, n. [Cf. F. opportuniste.]
   One who advocates or practices opportunism. [Recent]
   [1913 Webster]