1. FIA Formula E Gen2 EVO a.k.a. Spark SRT05e 2.0 (recently)

Unveiled in February last year and intended to use in service from 2020-21 season onwards but due to COVID-19 pandemic, the consequence was Formula E abandoned the Gen2 EVO and ended up stalled in service. The Gen2 EVO design removed the closed wheel, twin rear spoiler and also shark fin.
2. Falcon Indy 01-A

Unveiled in early 2003 and intended to raced in IndyCar Series in 2003 with an F1-style nosecone even nose pillars but sadly never raced due to lack of room in IndyCar Series and Falcon Indy 01-A also ended up stalled in service.
Any additions?