Well it depends on what t-maxx (2.5, 2.5r, 3.3) and how it's going to be used. On my 3.3 for instance I use it for bashing and jumping so I went with trx steel center driveshafts, rpm a arms, aluminum bulks, rpm axle carriers in the front, rear rpm true track conversion which replaces the rear a arms and axle carrier with the true track which eliminates the toe links, Big bore shocks and integy 40 spring progressive rate spring set with different stiffnesses, aluminum diff cup conversion in the front which uses a stronger diff cup than the stock plastic and 3mm screws to hold the ring gear rather than the stock 2mm, in the back I put in a spool since I run off pavement, I drilled out the diff cup and tapped it for 3mm screws and drilled out the ring gear holes (you need titanium bits since the ring gear is hardened), rpm front and rear bunpers, and rpm skidplate covers that install over the stock skidplates, Aluminum chassis braces and tranny skidplate. You can also do a foc conversion for more power and less rotating mass in the tranny but I opted not to at this time since as a basher I use reverse a lot rather than walking across the 'track' (aka dirt mound) to get unstuck. I also run a 19tcb and 58t sg for ripping accel in the short runs before a jump.if you do this you need to adjust the shift point in the tranny and it will considerably lower your top speed but it is ideal if you have limited space and don't run long distances for top speed.
That's all I can think of for now....
Oh, I also got a glow plug igniter and pull start and eliminated the easy start to save weight. I also installed a hitec 645 high torque steering servo and moved the stock 2055 servo for the throttle/brake since it is higher torque than the stock 2018 servo which will provide faster throttle and firmer brake control. Aluminum servo brackets because with the high torque servos the stock plastic mounts tend to twist. Also on the brake servo linkage you can replace the length of fuel tubing with a stiff spring, I used a piece of spring from an old servo saver.
These are all different hop ups and mods you can do for a basher.
