Coming from a trout background using flies and inline spinners I've never had use for terminal loop knots. Now that I'm learning to fish for bass and crappie I do.  (Admittedly there is a loop not used for dry flies but I never learned it or used it.)

 

Are there more than one of these loop knots? Are any of them more reliable than others? 

 

I look forward to your replies and learning how to tie a loop knot. 

I use the rapala loop on small cranks/jerkbaits. 

 

lefty loop for me when I use a loop knot on conventional.  I prefer it over the rapala knot as it creates a streamlined tag end.

I use a Rapala Knot for my jerkbaits and a San Diego Jam Knot when trying pretty much everything else.

The Lefty Kreh loop knot is the epitome of loop knots. 
 

BTW, his leader knot is darned good, too!

I did the Rapala loop knot for many years.  It's a good knot for bass fishing lines.  However, I eventually made my way to snaps and typically use them in places where I would have used a loop knot in the past.  They're quicker, more convenient, and provide just as good of action.  Get the VMC Duolocks if you're worried about adding weight.  They make a 30# version, which probably won't last much beyond 20#'s, that's super tiny and weighs next to nothing.  They're plenty strong enough for use with the 10-16# line that I use them with.  

Anytime Im fishing vertical, using a light swimbait or fishing in any kind of current I prefer to use a loop knot.  It allows the bait to articulate freely without a fixed anchor point on the eye. I do feel like loop knots arent as strong as a fixed knot.  I just try to keep an eye on every so often and make sure theres no damage or hard kinks in the loop.  

Used to use the Rapala Knot, but found the non slip loop to more then serviceable even for big plugs and the downward facing tag means you don't ever have to pick grass out of it.