Surprisingly, the one I shoot often most is also my one of my cheapest:

PSA Lower
PSA Mid-length M4 Upper (stainless)
PSA Carrying Handle
PSA No-Logo C-158 BCG
PSA EPT***
MagPul MOE Handguards
MagPul MOE VFG
Milsurp A1 - yes, A1 stock
SOB B-Sling
SIG Ambi Mag Release
Generic Ambi Safety
BOTACH/KZ Sight Tower Combo Mount https://botach.com/kz-ar15-m4-sight-tower-combo-mounts/ (linked because I think it's the shitz)
OLight Valkyrie WML

I've mentioned this before in threads, I built this to troll Eurodriver when he was going on about driving over his 6920, hence the PSA parts. When I took it to the range to function test and zero, I liked the way it shot so much that I decided it was not going to be subjected to the run over on a sandy road torture test. Once I decide it was a keeper I added the light mount, SIG ambi release, swapped the PSA EPT (which was nice enough) for an MBT 2 and put on the A1 stock, which I got from Numrich.

I modded the carry handle for a 100 yard zero using the RIBZ method( https://www.m4carbine.net/showthread...061#post798061 ) and put in a round 'match' front sight post.

Fun rifle to shoot, I swap between the Romeo and the Carry Handle, with no big zero shifts, but I do generally re-zero @ 100.

In today's world, I shoot my .22 AR's a bunch more - because I don't want to dip below my reserve point of .223.