Polite but firm - I'm sorry, but you just don't float my boat
Helpful - Im not good enough for you.... but she is (point to the person you like least in the room)
Chav - f**k off n*bhead
Rude - Get lost dwarf/smelly/ugly/accountant (delete as appropriate)
You will have to face it socasa... no rejection you give is going to be accepted without any negative emotion. :) And lets, face it, we all take rejection personally.... its only human.
Whats the way you would most like to be rejected? Thats probably the best way to deal with it....