What are the best out there?

Tower defense?

Bloons TD6 is a crap ton of fun, but I think it costs like 6$. But I’ve put hundreds of hours into it and still enjoy it.

Yes tower defense, ah 6$ i thought that was free to play. I guess i'll have to try it. Does it have Co op?

The co-op one is actually free to play

Rush Royale is a decent play. Free to play. Can buy passes for double rewards and so on. Worth a look, has pvp and coop, plus regular events and clan matches