t1 arty is very good vs megalith or yuthota, and does ok vs other t4 too
t1 light bots are pretty good vs percivals or obsidians
t1 sera arty can work well vs aeon navy to buy time
t1 land scouts are pretty good to draw fire from fatboys (most importantly enemy thinks that their fatboy is shooting and doing something useful, but in reality it can just be t1 land scouts)
t1 air scouts are very good, t3 are better ofc, but they are also expensive. you often need t1 air scout vs stealth or to just cover whole map with them
t1 engineers are still good, especially cause you can spread them out to collect reclaim in large area, and don't need a t2 or t3 factory to make them
and that is why t1 bombers are still good too
t1 bombers are pretty much always good when there is no AoE antiair damage (but can be bad vs fast moving targets or when you need a sneaky attack. You can miss single strat bomber but flock of 100 t1 bombers will get noticed)
t1 subs are good vs t2 sera navy (especially sera subs in big numbers)
t1 cybran land scouts can pretend to be firebeetles to scare opponent
t1 light bots are good as a part of a ghetto gunship
t1 interceptors are good for killing engineering drones (afaik ASF don't target those)
you can put t1 subs underwater where usually commanders hide and that can trick your opponent
t1 frigates are pretty good vs battleships
t1 sera air scouts leave 10 seconds of vision after death, can be exceptionally helpfull vs stealth
t1 sera land scouts can hide and stay hidden and provide vision in lategame (but they often get reclaimed tho)
t1 aeon land scouts work well as fake targets in navy fights
t2 cybran mobile stealth is pretty convinitent cause you can put it in transport (and it will keep woking) or put it into dence bases to not waste space on stealth generators
t1 air transports maybe slower and can carry less, but they are cheap and still functional in late game, especially for dropping engineers on reclaim