There's a common expression "save the best for last." That's probably what you mean to say.

J.K. is right. When you say "save the best for last", "last" is a noun. You can even put "the" in front of it without changing the meaning: "save the best for the last". However, if you say "save the best to last", then "to last" will be interpreted an infinitive verb form. It would mean: save the best in order to last a long time.

"Last" is a flexible word that can be a verb, noun, adjective, or adverb. Here are some examples: "Save the best for (the) last" NOUN "Save the last one for me" ADJECTIVE "Save the best one to last the longest" INFINITIVE used to create adverbial clause "The best lasts longest" VERB "Mike last ran in the race a year ago" ADVERB (meaning he hasn't run for a year now) "The potato chips are good to the last" NOUN (because "the" prevents it from being interpreted as a verb.)