AW IMR High Drain 18650 or PANASONIC Hybrid IMR CGR18650CH.
AW IMR are a safer chemistry and designed to handle high drain.
The Panasonic CGR18650CH is a hybrid, technically not IMR but gets called IMR - also a safer chemistry.
Those are the better two options.
I suggest you read the ECF guide on batteries:
http://www.e-cigarette-forum.com/forum/ecf-library/129569-rechargeable-batteries.html
It says this, among other things:
We suggest the best option, in order, is:
1. AW IMR Li-Mn rechargeables.
2. AW Li-FePo4 rechargeables [Li-FePo4's MUST HAVE A SPECIAL CHARGER]. Note that these batteries are mostly 3 volt nominal so the system voltage will be lower than normal.
3. Good quality (such as AW or Pila) protected Li-ion rechargeables.
4. Branded protected Li-ions come next - such as xxxfire Li-ion rechargeables (for xxx insert Trust / Sure / Ultra-).
5. The least-preferable option is a generic protected Li-ion.
6. Unprotected rechargeable Li-ion cells should not be used.
7. Standard cells (non-rechargeable) should not be used.