For me, it's both of Bruguera's groundies. He had the wristiest, most ideosyncratic forehand technique in history in my opinion. There have been lots of big western forehands over the years, but they ALL use that generic windshield wiper technique, except for Bruguera.
For me personally, I like seeing self-choreographed technique, the kind that cannot be taught. And to me Bruguera's groundies exemplified that.
I just think his forehand in particular, it was like a marvel of egineering, the eigth world wonder to me, that he was able to pull that contortionist style technique off against pro level pace...on a scale of one to ten, I'd give it a 14+ in terms of how difficult I think it is to try and copy this stroke.
Also, his backhand was also entirely unique. Most backhands have that generic straight take back technique. Rios did too, it's honestly techinquely no more unique than say Kiefer's backhand. BUT Rios was just a naturally stylish guy, like on So You Think You Can Dance, they always say about how some of the dancers, they're just naturally "cool." That's just how Rios was, a James Dean type who didn't need to say much because the mere stare alone was enough, he was the pasa doble of tennis, the bull fighter, the cape, the glare, the snarl said enough...BUT his actual technique on the backhand was textbook, honestly not that unusual, it's just that Rios had his way of sweeping his cape that made it look just a little hotter than the rest...even though it's still just pulling a cape.
Bruguera's backhand, however, I admired because to me no one else has ever hit it like him, he invented his own technique...it wasn't merely a stylich but still textbook technique. As Cliff Drysdale once said, "Do you see how he takes the racket back, with the wrist cocked? It's a unique shot Patrick, it's a unique shot." Exactly. No one has ever used that stylish, regal BOX beam take back, not unlike his RD-7, preparation on a two-hander before to my knowledge. To me, he actually hit it with the same technique as a one-handed backhand, only with a second hand glued along for the ride. His technique was unique in that he prepared with a traditional, one-hander's closed, sideways, stance, and stayed that way through the contact point, again like a one-hander. Agassi in contrast, in particular, for example has more of a semi-open backhand stance preparation.
The thing is, this box beam take back actually adds nothing to the shot. It's just a unique ideosycrasity. In fact, if anything, I would argue that it actually HURTS the stroke in my opinion, robbing one of valuable time, and introducing a hitch in the motion. Nevertheless, his backhand was known as one of the best on tour per Peter Burwash ("one of the most versatile backhands in the game").
I noticed, however, that on the seniors tour and in the last match I have of him against Federer, he was no longer using the trademark box beam preparation nearly as much. He used to do it on virtually every ball which I always found remarkable, because having tried to copy that technique for years with much difficulty (put it this way, I found picking up a one-handed backhand as a life long two-hander much easier and more natural), I realize it really does rob you of time and requires more timing and EARLIER preparation. If you lose a step with this kind of technique, you're in trouble.
The thing is when I saw him play Federer, he was MUCH slower than in his prime, just coming off surgery, and moving with nowhere near the same confidence or anticipating nearly as well. He simply didn't get in position in enough time to take that unique take back anymore. Against Courier on the Seniors tour it was the same thing. He actually goes to the box beam take back only occasionally now when he has a plenty of time, otherwise he's simplified the stroke and now hits it more traditionally, i.e. the same ol' boring straight take back you see from every two-hander from Clijsters to Pierce to Capriati to Kiefer to Martin to Malivai Washington to Medvedev to etc., etc., ad nauseum, infinity. I must say I'm really dissapointed about this development. I liked Bruguera so much because I thought his technique was so unique and difficult to copy, time, and execute. Now that I see he's taken the easy way out on his backhand technique, by incorporating the simpler, less stylish but more efficient, straight take back swing; it's sad, because what made him unique is no longer there. It's like telling Sampras he can't lift his toe up before swinging on the serve, telling Becker there's a new "rocker rule," i.e. you can only rock back and forth two times before serving before the ref blows the whistle and the ball girls get to throw one ball at your private parts.
A little graphic, but you get what I mean. I like ideosyncratic strokes that I feel no one else on the planet can emulate or copy...ideosyncrasies that I think would make it FAR more difficult for the average person trying to hit these strokes to copy, but for whatever unknown reason it just seems to work for this particular pro only and no one else in the world.
To me, there's a few other "signature" strokes that belong on this list besides Bruguera's groundies, in no particular order.
1) Guy Forget with his hanging hind leg, grasshopper serve.
2) Edberg and the twitch your head to the side and look GQ for the cameras before you swing service motion.
3) The Becker rocker dropper (short for "rock 'em, drop 'em, SOCK 'em") service motion.
4) The Sampras raised toe, pigeon does what pigeon wants, service motion.
5) The McEnroe right angle triangle service motion.
6) The Bersategui Hawaain, "pinata" grip.
7) The Courier "Buff Bagwell" baseball backhand and pure MUSCLED, my jockstrap's too tight! forehand.
8) The Magnus Gustaffson chain-saw killer in a movie, slap-shot forehand hit with a Randy Johnson fastball meets a fat catcher's mitt type impact.
9) The Wayne Ferreira, the last South African cowboy standing on earth, lasso forehand.
10) The Seles Medussa like, two-headed, snapping pirranhas with a purpose two-handed forehand and backhands.
11) The Chang backdoor escape hatch, floppy wrist take back on the backhand.
12) The Kafelnikov my arms are so stiff they could be mistaken for crow bars forehand and backhands.
13) The Kaarsten Braasch lady bug that's been squashed and is squirming with its wings and eyes bugging out for dear life serve.
14) The Rios, Joey Casual sliding for home plate front foot first serve.
15) The Korda sword fish forehand swooping in for the kill, I also think the Korda condor forehand swooping in for the kill is another good analogy, also the venus flytrap looking for a bologne sandwich also works for me.
16) Am I missing anybody else?
17) Yes, that bisterd dey call me me in French. Pass the mustard.
Finally, as an addendum, I forgot one of my favorite signature (my definition of the term at least) shots of all time. The Goran serve. I've seen several of the newer generation try to copy his motion, and do it pretty good; but to me Goran's hamoc like, see-saw, swaying motion was something indicative of a perfect ocean breeze...so light, airy, and effortless yet so crisp in its impact that you'll not soon forget it...AND it can NEVER truly be recaptured or duplicated ever again, just like Saved by the Bell (there's only one Zach Morris.) It's what we neighbordhood kids around the Tennis Warehouse block call "The Wonder Years." Looking back, sigh, was something of a spiritual journey to watch Goran wind through his serve all those years. He kind of looked like a go kart racer from a Japanese anime movie flashing a Red Von Baron ace airfighter pilot for hire like grin before the start. And then, bam, the gun went off and you were left thinking gee this guy's got the rings of Saturn churning around his head like he's some kind of God who walks on air.
Funny, because I also tried to immitate Goran's serve for the longest time, and I had my good days just like I do with the Bruguera forehand and backhand; but I tell you, it really is a more difficult motion to time in my opinion than the more typical, textbook, Agassi style serve. On that, I kind of just think ok, throw ball up, bend knees, swing. On the Goran motion, you feel like you're performing lyrical dance with a partner you've never seen (call her a very beautiful, beautiful woman not unlike Alyssa Milano) for the very first time...on Star Search, and all the world is holding their breath waiting for either the ace, or more likely...the WHIFF, batter strikes out. Alyssa drops you like you're yesterday's news, and eyes Ed McMahon for a little sumthin'-sumthin'.
The weird thing is that in *almost* every case study listed above, these ideosyncrasies actually were their best or "signature" shots for the above aforementioned very successful pros. I kind of look at it like Minus' wet blanket, it's comforting to know that at least you're comfortable with your wet blanket. Why? Because that just means know one else wants to take it. No sir, that space of the universe is entirely reserved for you. Bombs away and happy million dollar earnings to you.
