Question

There are a number of theorems or lemmas or mathematical ideas that come to be known as eponymous tricks, a term which in this context is in no sense derogatory. Here is a list of 10 such tricks (the last of which I learned at MO):

• the Whitney trick
• the deTurck trick
• the Cayley trick
• the Rabinowitsch trick
• the Klee trick
• the Moser trick
• the Herglotz trick
• the Weyl trick
• the Karatsuba trick
• the Jouanolou trick

Edit: List augmented from the comments and answers:

• the Eilenberg–Mazur swindle
• the Parshin trick
• the Atiyah rotation trick
• the Higman trick
• Rosser's trick
• Scott's trick
• the Craig trick
• the Uhlenbeck trick
• the Alexander trick
• Grilliot's trick
• Zarhin's trick [For any abelian variety $A$, $(A \times A^{\vee})^4$ is principally polarizable.]

Further Edit. And although my original interest was in eponymous (=named-after-someone) tricks, several non-eponymous tricks have been mentioned, so I'll gather those here as well:

• the determinant trick
• the kernel trick
• the W-trick

Some of those listed above do not yet have Wikipedia pages (hint, hint—Thierry).

I (JOR) am not seeking to extend this list (although I would be incidentally interested to learn of prominent omissions), but rather I am wondering:

Is there some aspect or trait shared by the mathematical ideas or techniques that, over time, come to be named "tricks"?

I am aware this is a borderline question; feel free to close if it unduly distracts.