Adding a simple "The" solves that problem.
"The Toy Cannon", incidentally, is the nickname of 1960s-70s Houston Astros center fielder Jimmy Wynn. He got it by hitting moon-shot, tape-measure home runs despite being (charitably) 5'6" tall. The name itself has no relation to this blog save for two things.
First, we'll be talking about baseball. Not all the time or anything. But it'll come up.
Second, as nicknames go, that one is absolutely perfect. I mean, boy, is it ever perfect. We've entered a real down-time in terms of nicknames and I worry that it's a permanent thing. Look, the best player in baseball right now is Alex Rodriguez. Fifty years ago, he would have been called something like "Moonshine Al" or "The Impossible Machine". Something evocative, you know? The best we've come up with for him is "A-Rod", which tells you bloody well nothing. If you were looking at Jimmy Wynn up at bat and asked who he was, and I told you "Oh, that's Jimmy Wynn, the Toy Cannon", I suspect you'd have a good idea of what he was like as a player. Not so with Alex "A-Rod" Rodriguez.
That's not his fault, incidentally, horrid Yankee though he be. The "X-Rod"* nicknaming convention is insidious. Ivan "Pudge" Rodriguez had a great nickname (though stolen a bit from Carlton "Pudge" Fisk), but I've heard people refer to him as "I-Rod". For shame, people.
*This same problem extends to politics. Otto von Bismarck was "The Iron Chancellor", which is kickin' rad. George W. Bush is "Dubya". Christ. It's just his middle initial, mispronounced.
For my money, the top ten best nicknames in all of history are as follows:
1. Edward "The Black Prince"
Just an absolute stunner of a nickname. You have to marvel at how badass a man has to be to be nicknamed "The Black Prince". I can just imagine the conversation back in France:
French Soldier 1: So, I hear the English are coming. We can totally take them. Who's in command?
French Soldier 2: The Black Prince.
French Soldier 1: God damn it.
French Soldier 2: I know!
For what it's worth, Edward was never called "The Black Prince" in his lifetime, so the above conversation never really could have taken place. Still. "The Black Prince". Damn, son.
2. James "Cool Papa" Bell
This nickname is good enough that it's subsumed James Bell's actual name; I know an awful lot about baseball*, and I had to look it up. Cool Papa Bell was a Negro Leagues great, said to be so fast that he could flick a light switch and be in bed before the room went dark. The marvelous part about this legend is that it actually happened once, due to faulty wiring.
*God, I'm so smart.
3. Jimmy "The Toy Cannon" Wynn
Covered previously. Jimmy Wynn played in a cavernous pitcher's park in a low-offense era that killed his chances at the Hall of Fame. One year, he alone accounted for 37 of his team's 93 TOTAL home runs. His wife also stabbed him this one time. So there's that.
4. Walter "Sweetness" Payton
Most football nicknames run the super-macho gamut; Mean Joe Green, Jack "The Assassin" Tatum, Jerome "The Bus" Bettis. Just saying "Sweetness" actually makes me smile a little bit. It's completely non-conformist, rolls off the tongue, and tells you all you need to know about the man's running style.
5. Attila the Hun, "The Scourge of God"
Visigoth Soldier 1: So, I hear the Eng--uh, Huns are coming. We can totally take them. Who's in command?
Visigoth Soldier 2: The Scourge of God
Visigoth Soldier 1: God damn it.
Visigoth Soldier 2: Also, we're about to enter the Dark Ages.
Visigoth Soldier 1: *forgets how to read*
Fun fact: Typing "Scourge of God" into Wikipedia takes you directly to Attila's page. You know you've a great nickname when no one has dared to take it for 1600 years.
6. Illich Ramirez Sanchez, "Carlos the Jackal"
Leftist revolutionaries have a bunch of great nicknames (I'm not a huge fan of Ernesto "Che" Guevara, but you have to admit, that name has sticking power), but Illich Sanchez' is the best. Reduced slightly in power considering the guy is in prison and did not die in a hail of gunfire.
7. Martha "Calamity Jane" Cannary
Another nickname that has completely subsumed the subject's actual name. Whatever your opinion* of Calamity Jane, it will change dramatically once you watch HBO's "Deadwood".
*Unless your opinion of Calamity Jane is that she is a drunken mess of a person whose every other word is a profanity. Then your opinion probably won't change much.
8. Manfred von Richtofen, "The Red Baron"
English Pilot 1: So, I hear the Germans are coming. We can totally take them. Who's in command?
English Pilot 2: *dies of trench foot*
English Pilot 1: God damn it.
9. Erwin Rommel, "The Desert Fox"
Are there foxes in the desert? I think there are, but I'm too lazy to confirm that independently. I doubt they're really all that fierce. Anyways, I hate to give a great nickname award to a Nazi, but "The Desert Fox" is too good to pass up.
Is a movie made better by the inclusion of the Nazis as the main villain? I'm pretty certain that's true, based solely on the Indiana Jones movies. The first and third? Excellent. Lots of Nazi-punching/shooting/dissolving-due-to-the-terror-of-the-Almighty. The second one? Tribesmen. Not so good.
10. Bob "Death to Flying Things" Ferguson
19th-century infielder who apparently was very good at catching spherical white objects before they hit the ground. This nickname is really long and wordy, which is usually the worst thing a nickname can be, but it's just so goofy that it gets the nod. It's one of those things that only drunken men with bowler hats and handlebar mustaches could come up with.
That's a hell of a list.