I accidentally bought 5l of Tygris T515 Moly cutting fluid so that's all I try to use, since it was quite expensive!
The "best" stuff I've used is HMT Speedlube, it's worth every penny. My brother uses it exclusively.
1. it comes in aerosol so no faffing with tins and squirters etc.
2. it foams so it stays in place much better than normal lube on vertical or upside-down surfaces etc. The foam dies back fairly quickly but it's "just right".
3. the actual cutting lubrication is fantastic, you can almost feel a mag drill bite in faster when using it.