I ordered a series of 9v batteries for my Silver Pulser, here how they all ranked up.
#1 - Best - http://www.ipowerus.com/
520 mAh Lithium Polymer (Rechargeable)
The Lithium Polymer recharge extremely quickly, have tons of voltage, and last longer than a non-rechargeable battery, about 16 hours. This one will make your hand dance!
#2 - Good - http://www.onlybatteries.com/showitem.asp?ItemID=14671.11&cat1=14&uid=1970
400 mAh Lithium Ion (Rechargeable)
The Lithium Ion batties recharge about half as fast as the Lithium Polymer ones. They will last about 400-500 charges then die. They do not have the same voltage as the polymer, but are still good. Lasts about 10 hours.
#3 - Average - standard non rechargeable battery (12-14 hrs)
Most of these last fairly well and have good voltage. Costly as you cannot recharge them. Last about 12 hours.
#4 - Total Crap - Energizer
150 mAh NiMH (Rechargeable)
Worst batteries I've ever used. Last about 4 hours, take forever to charge (12 hours) and do not crank much voltage. Save your money, these are a scam, like all energizer products. They are the most expensive of the bunch too, wonder what the bunny was smoking.