1. Is he an ex, a friend you used to date, or a friend you used to bang?
How do you talk about this person? Is it as a good friend, or as an ex? Do most of your other friends even know that the two of you once dated? If you primarily think of the person as an ex, you may want to leave him off the guest list.
2. What are your motivations?
Why do you want this person at your wedding? If there’s any part of you that's thinking, "That'll show him" then not only should you not invite him to your wedding, you might want to give some serious thought to whether or not you're ready for that wedding!
3. Is he a sloppy drunk?
If there’s any chance that he will make an anatomically specific embarrassing toast or declaration at the wedding, keep him off the guest list.
4. What does your fiancé say?
No matter what the answers to the above questions, the final call is your fiancé's. If he is uncomfortable having the ex at the wedding, the answer is no.
One more note, you and your fiancé aren't the only ones with complicated feelings here. The ex might be a little conflicted as well. Don't be surprised if your ex turns down the invitation. NEVER try to talk an ex out of this decision (see question number 3).
What do you think? Would you invite an ex to your wedding?