I am a menthol junkie, and after long and extensive research, there are two juices that I love:
1. Mister-E's Menthol...33% VG, Full Flavor, and I always ask them to add extra menthol. This stuff is GREAT, and it works really well in carto's. A K808 carto will often last up to a month with Mister E's Menthol. The taste is strong, smooth, cool and a little bit creamy (for lack of a better term).
2. RW Vapors' Menthol Extreme (formerly Vapors Etc.)... no sweetener, no flavor boost. This stuff is HARDCORE, and it also works very well in carto's. It's not "creamy" like Mister E's Menthol.
Both of these are straight menthol, with no sweeteners, mint or
tobacco flavoring, and both are like a good old fashioned menthol punch in the face.