Using letters:
* Wot (a common British slang spelling)
* Wha (short and punchy)
* Whut (more informal)
* Wat (a more modern, abbreviated spelling)
Using sounds:
* W-h-a-t (emphasizing the sound)
* Wh-a-t (similar to the above, but shorter)
Using other words:
* How (depending on the context, this can be a suitable replacement)
* Which (similar to "how", it can also be used in place of "what")
Using symbols:
* ? (the question mark, directly representing the question)
* 🤔 (thinking face emoji)
The best way to choose a creative spelling depends on the context and desired effect.