I've floated this in discussions a few times, thought about it a lot, and come to the conclusion - if there's anything that's justified in being added as a 17th skill, it's a Fencer - I'm not sure where I got that name from (L2? Hamsters? Clones? Not really sure), but it would basically be a destructive skill that creates a tunnel at an upwards angle - essentially a miner, but in reverse.
What I'd like to discuss on this (and it may be a while - possibly including later than just at the big update - before it actually gets implemented, so there is plenty of time to discuss these things) is:
1. Do we want to (without considering what they may be) add any further skills at all? We don't want to end up like L2, but on the other hand, while some of the first 8 new skills might not be too useful *coughstackercough*, in future any new additions would be much less rushed - as can be seen from that this is the first time since V1.16n that I've proposed adding anything more.
2. Assuming we do want to leave open the possibility of more skills, is Fencer a good choice? Keep in mind that essentially, it would be like a miner that starts from the bottom instead of the top. However, this alone may be worthwhile because while we currently have horizontal, diagonal-down and vertical-down skills, we don't have any destructive skill that goes upwards (unless you count the bomber).
3. And finally, if we do implement it, how exactly should it work? For example - how many "slashes" can he take without moving upwards before he gives up, or should he be able to keep going (essentially acting like a basher) even without upwards movement, just as long as he destroys something and hasn't hit steel? Should we introduce one-way up arrows that are only destroyable by the fencer (and perhaps any future skill that also destroys in an upwards direction, though I don't see a very high likelihood of introducing any others)? Even the finer details of the masks - should the terrain removal be from bottom to top unlike other skills (which also gives Fencer another unique property compared to miner or basher, in that it can't be used to create staircases by interrupting mid-stroke)?
I want to stress again that this is not a gateway to suddenly exploding to L2-like quantities of skills. Like this one has been (and will continue to be, via your input now rather than just mostly my own thoughts), any additions will be carefully considered, and quite possibly even trialled before officially introducing them into the game; and I don't expect them to become a very regular thing - as I mentioned, this is the first new skill I've considered in a long time. I know I've repeated this point many times, but I feel it's important to do so, as I don't want a potentially useful skill to be rejected just because people are afraid it will open the gate to an influx of relatively useless ones like L2.