Black and Decker 36V Lithium Trimmer LST136
I looked at that trimmer in-store before I eventually bought my 18V Ryobi. After using (and really liking) mine, which has plenty of power, I think a 36V model is overkill for only a trimmer. If you weren't planning on buying any other tools that use these batteries, I'd look at an 18 or even 24V trimmer - they're cheaper up front, and cheaper to replace the batteries. On the other hand, if you want to buy multiple tools, then the power of 36V might be the wiser investment.
As an example, my trimmer came with a free leaf blower, and I also bought the hedge trimmer. All three tools use the same 18V batteries. While the blower and hedge trimmer have just enough power for my uses, I can see where being merely 18V would be quite underpowered in a lot of situations. Power shouldn't be an issue for a 36V line of tools.