In roughly descending order of how much they piss me off

1. "It's a legal issue" (Almost never from an actual lawyer or even someone who has talked to one)
2. "It's an antitrust issue" (Specialization of legal)
3. "It's a bizops issue" (Generalization of legal)
4. "It's a scale issue" (Or "that costs too much cpu time / disk space")
5. "It's a perf issue" (Same as above)
6. "It's a privacy issue"
7. "It's a security issue"
8. "[Exec XX] just doesn't like it that way"
9. "It's a test bandwidth issue"
10. "What's the market size?" (An argument you can never win unless someone else has already done it - at which point the assumption is always that we will win all existing market share but never that we will grow the size of the market.)
11. "Do you have a fully detailed business model?" (Often by the time you get this done, you could have just launched the damn thing)
12. "Have you done focus groups / user testing / market research?"
13. "We're fully booked until 2006"
14. "We're fixing that in Longhorn"

Related statements (Contributed anonymously)

1. "We should do it this way instead" (at the 11th hour from the guy who never read your e-mails or went to the meetings)
2. "Can you keep me in the loop on this?" (From the guy who will become the guy in number 1.)

Oliver Roup (2004)