I tend to agree with Kup that sometimes the packaging, promotional or trademark issues sometimes put a toy at odds with the original design. (RTS Wreck-Gar or G2 Prime are clearly "classics" toys for instance).

As a kid I repurposed toys from otherlines as Transformers too. Many of my hot-wheels cars were substitutes for Autobot cars I didn't own. My Machine Man Man-o-war was Broadside.

It's interesting that every example so far is people repurposed toys to be "Classics". A couple of examples of my repurposing that aren't are:

Sidearm Sideswipe is my Movie Sunstreaker
"While his identical twin brother Sideswipe prefers to get up close and personal in battle, the vain Sunstreaker prefers to keep his armour clean and pick off Decepticons at a distance."

"Rally" Sideswipe is my Movie Bluestreak
"Before the war Bluestreak was a racing champion, highly competitive with fellow racer Sideswipe. Since the destruction of his home-city, Bluestreak only cares about winning one thing - the war against the Decepticons!"

(I'd actually like to give both new heads and a bit of a tweak to their colours, but the in the meantime, this justifies me having three deluxe Sideswipe toys)