Luckily my worst saboteurs are my coworkers and I dislike most of them anyway...
Here are my favorite saboteur tactics:
"You look fine the way you are, why are tryign to lose weight anyway?"
"Oh, this one little cookie/cake/candy/lardbar won't kill your diet, c'mon."
"You are doing so good, why not let yourself splurge a little?"
"Don't be stubborn it's only (fill in the blank)."
"Are you sure you don't want some? It's soooooo goooood...." (Someone at work actually used this on some pizza that caused food poisoning the previous day but she was still eating it!)
Most saboteurs don't mean to be so darn evil but it happens. My boyfriend is super supportive and non-judgemental but once in awhile brings in Haagan Daaz or my best friends (Ben & Jerry) as a reward food ("this is for getting through your first week of school.") and if I've got calories to spare, I indulge. If I don't, I give him a kiss and tell him to hide it so I don't see it.