Vertical Spinner
Real life examples: Nightmare, Backlash, 259 Game examples: Ripblade, Ninja, BOT-204
A kind of bot with a Vertically spinning weapon.
VS (Vertical Spinners) tend to be unstable, and can easily be knocked off balance. The pros of VSs are they do pretty decent damage, and can fling robots in the air, something HSs (Horizontal spinners) cannot usually do.
Building a Vertical Spinner
If you are building a VS, you will probably want to focus most of your weight to your weapon, and make sure the bot has enough support. You could use snowplows at the sides or your bot - becuse most VS have issues turning while spinning their weapon.
Be very careful about weight distribution on a VS. That is, try to make your bot as symmetrical as possible.
VS Designs
Angled design
Yes, it is possible to achieve an angled design like Nightmare. I would suggest having a look at Alien Queen in the Starcore AI packs.
Angled designs do not need wedges and the chassis isn't easy to hit, nor the weapon motors. They have somewhat less issues turning because they have a wide stance.
The main issue here is the frontal wheels... these are candy to a HS and if one gets ripped, you'll be unable to move in a controlled way, and your spinner will stop. (worse than Ripblade)
Wedged Design
It is also a good idea to have a nicely built wedge so you can get under your opponents and hit their vulnerable underside. This is clearly the better tactic for a VS.
The wedged design comes with a wedgelike chassis (obviously). Add small wedges on a burst motor for getting under your opponent, and add spinners to the top of your wedge.
VS Weaponry
It depends of your tastes. Use a HP Z-tek for weapon (yes, you can even on LWs)
Disc VS
Disc VS, as their name implies, do feature a disc on a motor and ideally four weapons.
Use irons if you can, or razors, but your disc won't last long then. Don't use blades like on Ripblade-they suck. A good though odd choice is spiked clubs, like on undefeated Insult to Injury V
Disc spinners aren't very damaging, but they reach quickly maximum rotational speed (AKA "have a short spin-up time"), hit often and are very hard to stop.
Tribar VS
Uses pretty much the same weapon design as a good horizontal spinner, only vertically mounted. Use a tribar on your weapon motor, and add one (or several) weapons on each of the three APs. Your weapon will be tall -beware-. You will get fewer hits, but more damage and more knockback effect because the weapon tip carries more kinetic energy. Beware, the tribar design can be easily stopped and has a longer spin-up time than the disc design.
Bar VS
this variation is not seen often but a bar VS uses extenders instead of a disc/Tribar. this kind of VS is recommended if you want to try and build a BW vs or are really pushing the weight limits on a LW.