I like Fusion Bolt, Fusion Flare, and V-Create because of the cool animations (lmao), and Acrobatics and Volt Switch are two moves I've used a lot ever since they were introduced.
Oh, and lastly - I mentioned Low Sweep because I have a lot of funny memories associated with it. I used Weavile a ton in Battle Spot last year, and whenever an unsuspecting Tyranitar (or any other Pokemon 4x weak to Fighting) switched in, I'd proceed to obliterate it with Low Sweep. Those were good times.
I agree with those signature legendary moves. Fusion Bolt and Fusion Flare had a unique gimmick in that one of the two moves get powered up after the other is used, sadly both Reshiram and Zekrom resisted them so it was a bit worthless. In double battles however, have the two dragons together and the one who attacked second can really demolish the foe.
Acrobatics is a really good move, to the point I intentionally don't give any held items to a Pokemon that knows it solely for the power boost. I also love how quickly the Pokemon moves in the animation, sorta reminds me of a ninja.
Low Sweep was once a great move for Technician users, such as Breloom or Ambipom. It was sad to see the move's power increased in 6th Gen and therefore lose its Technician benefits but it's still good for slower Fighting-types since the Speed lowering can make a difference.
I have some kind of strange fascination with Heat Crash. Maybe because the Fire type is my second favorite type, and I'm a sucker when it comes to fire. I love fire. I'm not a psycho though...stop looking at me like that. ;-;
I wonder if you knew it was the signature move for the Tepig line? It does at least give something to make the fiery pig stand out, since the other two Unova starters never really had a technical signature move. Oshawott is heavily associated with Razor Shell and Snivy with Leaf Tornado but there's a few other Pokemon who also learn those moves so you can't really count them as signature moves.
Speaking of Razor Shell, it is one of my fave moves ever, but you likely already knew that.
I would say Electroweb. It's the first thing I would use in battle back in White 2 with my Emolga. I think it's one of Emolga's best possible moves. Kinda hard to get tho.
I have to admit, while Electroweb seems like a weak move, it does hit multiple targets which makes it handy in double and triple battles (and also hordes in 6th Gen). The move was quite limited back in B/W but B2/W2's Move Tutors did make the move far more widespread, such as having several Bug-types able to learn it.