When you get toward the end of a product, you have to make the tough calls about what gets fixed and what doesn't.  Most bugs fall into one of two obvious buckets:

• Must Fix -  Something is really bad here.  We cannot ship the product without fixing it.
• Won't Fix - The problem is minor, hard to get to, etc.  It won't be fixed for this release.

However, there are a few bugs which don't clearly fit these buckets.  There is no clear call to make on them.  My group has come up with some fun names for some of these bugs.  Among the taxonomy are:

• Yetis - These are bugs that you'd really like to fix but will be really difficult to find a fix for.  If you find a fix, you'll definitely take it but you won't hold the product until you find one.  Issues in this classification include areas where reproduction is difficult.  Stress crashes, random lockups, and inconsistent behavior all fit into this category.  We thought of using the term Sasquatch but that is too many characters.
• Limpets - These would be more accurately called Remoras, but why we don't is a long story.  These are bugs that we'd really like to fix but it isn't worth the risk to take a change to a particular binary or even the whole product just for that fix.  Taking a change to something already considered done requires another build, test pass, etc. 
• Sharks - Remora are also known as suckerfish.  They are known for attaching themselves to the side of a shark.  The idea here is that, while we wouldn't crack open a binary for a limpet bug, if there is a large fix which must go in, we'd like to take these other bugs with it.  Once you have started changing things and have to redo your test pass, you might as well include those nice-to-have issues too.

What nomenclature do you use to describe bugs?