The X-Men have many characters, but some are so popular that they dominate the answers of "Favorite X-Men". While what qualifies as "mainstream" will vary based on the person, I'll let you judge for yourself. Generally, if they're on a '90s Jim Lee poster, they probably wouldn't count. These are people that some rando on the street or someone with only a superficial knowledge of X-Men are likely unaware of.
I'm talking about characters such as:
Warpath
Wolfsbane
Blink
Marrow
Forge
Longshot
Sage
Bishop
Chamber
Cannonball
Maggott
I think you get the idea. Also, not just the X-Men, but their various splinter teams count as well.
So who are your favorite non-mainstream X-Men? Discuss.