[Raynian]

Alright, this shit is weird.

Putting

slot3
slot1

Will bring up the wrench on spawn and switch to the shotgun.

slot1
slot3

Will do the same, though.

Got the same thing with wait commands.

Messing around with other shit though, I got this

slot3
bind q "slot1; bind q lastinv"
bind 2 "slot2; bind q lastinv"
bind 1 "slot1; bind q lastinv"

The last line is just a failsafe.

That spawns me with the shotty, lastinv defaults to the wrench, and if I ever switch to the railgun it will properly treat that as the lastinv weapon used.

You probably want something more along the lines of

slot3
bind mwheelup "slot1; bind mwheelup lastinv; bind mwheeldown lastinv"
bind mwheeldown "slot1; bind mwheelup lastinv; bind mwheeldown lastinv"
bind [ "invnext; bind mwheelup lastinv; bind mwheeldown lastinv"
bind ] "invprev; bind mwheelup lastinv; bind mwheeldown lastinv"

Don't forget to put bind q lastinv in your userconfig.cfg so your other classes don't get screwed.

Let me know how that works. I use the default number keys + Q as lastinv, but use binds for sentries/dispensers so I don't know if you want any further changes.