First game bought in Steam.

Left 4 Dead Bundle

counter - strike 1.6 in 2005 =)

The orange box in early 2005)

The first one was L. A. Noire

CS:GO XD

My first was - GTA5 ONLINE

My first Rust. Then DayZ, then counter strike Pak.
For the first two a little sorry for the money spent, because, as it turned out, they need to cuddle up with friends, but the COP was stuck with friends in the evenings.

To the moon Deep story, indie and a great soundtrack

My first steam game I bought for the winter 2018 sale, too tempting the price was - Sleeping Dogs: Definitive Edition.
And then the first activation key was Amnesia Collection which Humble Bundle were distributed free of charge.

The first was CS:GO, bought on summer sale 2015

Half-Life was the first game in the incentive even when steam was in this green interface, and only there. :)

CS:GO in the 13th year.

Metro 2033

Sonic Generations.

Pak overlord

Portal 1,2. Sold together, and the discount was

cs:go

Fallout 4

Batman Arkham City GOTY