opportunist

1 a person who dexterously and expediently changes or adopts opinions ever the opportunist, she immediately set about becoming the incoming administrator's new best friend Synonyms chameleon, chancer [British], acrobat, temporizer, timeserver, trimmer, weathercockRelated Words egoist, egotist, self-seeker; conniver, machinator, plotter, schemer

2 one who does things only for his own benefit and with little regard for right and wrong an opportunist who makes friends and then drops them as soon as they aren't useful anymore Synonyms bottom-feeder, chancer [British], self-seeker, temporizerRelated Words egocentric, egoist, egotist; conniver, machinator, plotter, schemer; barracuda, shark; hanger-on, leechNear Antonyms altruist