-Stacks3 from YourHead is a must. Partials, you can’t miss it.
-RWML from Tsooj Media.
The best stack for multi-lingual sites and client support from the developer Joost @Joost is great.
-NoLink stack and NoCurrent from Marathia Web Design are great.
-DoorKeeper is a great little stack again from Marathia Web Design.
The developer Jeroen @el_mourabbi offer superb support.
Check it out, great useful little stacks on Marathia Web Design (@el_mourabbi).
-Siphon from 1LD.
Great useful stack, just missing some features as Radio control, Checkbox and Attachments. This features are already on the 1LD Siphon demo site running on a beta version of the stack, It is still under development for future updates so has not been published yet. When this update/ features will be published Siphon will get a high place on the Extraordinary stack list. Good support from Jon Meadows and Skyler @1LDskyler.
-FormPlus from Chillidoghosting is great, just missing the feature to use it as a Contact Form without using the Steps and a Time pick at the Date pick. Support from Gregory @barchard is ok.
-Protect stack from Weavers Kingdom is a nice little stack which offer one page function (a single Protect stack for all elements in a page as text, images, whatever). Great customers requests support from @Lucas.
So many more stacks without going into detail.
-Most stacks from Stacks4Stacks etc @willwood stacks are a good option and a 10/10 support from Will. The CalcStack looking very promising too, specially as it integrate with the FormPlus stack.
-The Oak bundle from Yuzoolthemes is a recommendation, good support from Michael @yuzool.
… so many more to mention.