Char-gen: fully hybridized mix of MT/TNE/T4 -- background skills, higher education, and Entertainer career from T4 (mostly), contacts from TNE, everything else from MT (except for a little bit here and there from the T4.1 draft, some home-made bits, and perhaps (IIRC) even a couple little things from T:2300). Oh yeah, I've also reformatted all the rolls to match the task system.
Tasks/Skills: Tasks are pure by-the-book MT (IMO still the best, most robust, task system ever published for an RPG). Skill-list is MT, with additional Science types and the Performance cluster added from T4, and a couple other minor tweaks.
Experience/Improvement: Straight MT, but I've expanded MT's near-throwaway concept of 'Browine Points' into an additional 'reward' system to recognize exceptional/heroic efforts (a weaker version of the 'fate points' various other systems use).
Personal Combat: AHL/Striker with tasks & injury rules rephrased to match MT format
Psionics: MT (almost never actually used)
Worlds: MT, with stellar type fixes from TNE. Still vaguely considering going to something more 'scientifically accurate' (GT First In?) but for simplicity's sake probably won't
Animals/Encounters/Interpersonal Tasks: All by-the-book MT (though the first rarely comes up and I usually just wing the second)
Trade & Commerce: MT, including additions from Knightfall, but with per-parsec rather than per-trip rates (concept, but not details, lifted from GT Far Trader). I also make liberal use of the Exchange Rate Table from JTAS4/TCS/TNE (also in Striker, but with different values).
Ship Design: MT with fuel-usage rates changed back to match HG. Where exact crew/price/cargo values don't matter I'll usually just use HG to get something 'close enough'
Vehicle Design: MT as current default, but still exploring alternatives (maybe T20?)
Starship Combat: see Vehicle Design above
Travel: MT (but see Trade & Commerce above)
Equipment: MT as baseline, but willing to fudge just about anything, and have 'officially' declared CrImp1 = $5 US @ 2002 values (and see also Trade & Commerce above).
Large-Scale Combat: haven't decided yet; maybe MT, maybe Mercenary, might just wing it (almost never actually comes up)
Research: MT (does any other ruleset even have a system for this?)
Robots: haven't decided between JTAS2-4 & Book 8; also curious to see what T20 has (once again, something that almost never comes up).
Setting: Various -- CT-era Spinward Marches, Far Frontiers, & Reaver's Deep; MT-era Gateway Sector (from MTJ4) & semi-canonical home-brewed Massilia (AotI & Knightfall as baseline, with various minor & semi-major tweaks); very much looking forward to M:1248 and Interstellar Wars era (the latter not-yet-announced outside of my dreams).