Here's my best I've seen live XI. For the sake of this I'm rating exclusively on performances in matches I was at, and where I can recall which day I was at I've limited it further. Bonus points for memorability.
1. Sir Alastair Cook - 53 vs Somerset, 2019
Memorable firstly for the fact that he appeared to be batting on a different pitch to everyone else all through that match. Memorable secondly because it turned out I was staying in the same hotel as the Essex players and walked in the door directly behind him. It was so, so obvious that he was a ATG-level bat amongst mere County mortals here - had so much time and nothing phased him. Crushed the dreams of Somerset fans everywhere, but nobody held it against him. Came out of the dressing room to give his batting gloves to a young girl at the end of Day Four. Hero.
2. Ajinkya Rahane, 118 vs New Zealand, 2013/14
Looking back at the scorecards, I think I've literally never witnessed openers make big runs. So I'm converting Rahane here, mostly because his ton >>>>> Dhawan's 98 in the same innings and the only other obvious conversion was Shaun Marsh going from 98* to 156 in the 2017/18 Ashes. Rahane is much more likeable, and this was a genuinely good knock that I remember very little detail of, other than the fact it was a really good knock.
3. Jacques Kallis, 111 vs Australia, 2005/06
I'm 10 years old, it's Ricky Ponting's hundredth Test, I want to see some great cricket from Australia. Alas, Jacques Kallis and Ashwell Prince bat all ****ing day. South Africa are finally dismissed late in the day, we leave early to beat the traffic and miss a handful of overs faced by Hayden and Langer. Memorable for it's sheer tedium, and the absolutely trolleyed blokes in the bay next to the Alcohol Free section I was sitting in using a *** doll as a beach ball substitute.
4. Steven Smith, 171* vs Hawkesbury, 2009/10
Not exactly his, uhh, strongest opposition ever but there was something especially fun about watching SPD smash it to all parts years before all you ****s got on board and accepted him as the incredible batsman he is. Was there with a mate and at one point yelled out for him to hit us a catch. Probably a coincidence, but a handful of balls later a reverse leg glance sailed five metres over our heads into a bush. Pretty sure I've also seen him make a few 80-odds and bring up his ton against India in 2014/15, so he gets the nod here.
5. Henry Nicholls, 145* vs England, 2017/18
Toss-up between Nicholls and Williamson here, but I wanted to go with a specialist middle order player rather than shuffling Kallis down to 5. This one's particularly memorable for the time spent discussing and analysing Nicholls' technique, and seeing the results when he managed to get all of the moving parts right.
6. Andrew Symonds, 162* vs India, 2007/08 and taking a stand against the scourge of racism
Look I remember nothing about the innings aside from being very confused when there was an extended delay where the umpires stood around looking very serious at Harbhajan and co, and that Brad Hogg made some great lower-order runs down the other end. I'm giving Symonds the nod in a tough three-corner battle here - other competitors were Moises Henriques for his 161* vs Tasmania in 2012/13, where he batted to his full potential and punted a few blokes over the stands at Bankstown Oval (IIRC), and Mitchell Marsh's maiden ton in the 2017/18 Ashes that I'd really, really, really hoped were vindication and him turning a corner (alas it was not, so the innings has since lost its #narrative points).
7. Peter Nevill, 83 vs England XI, 2013/14
Also for top-scoring with 66 and his 7 dismissals in the D/N Test vs NZ. He came in at 5/93 against Broad-Rankin-Finn-Swann and put on 180-odd with Ryan Carters, as captain, and making tough runs. It wasn't a memorable knock, as such, but the value of Nevill has always been his Woakes-esque lack of memorability and consistent un-***y solidity. Undervalued, underappreciated, underrated player. Also a cracking bloke when he came along to our club's presentation.
8. Ishant Sharma, 6/51 vs New Zealand, 2013/14
I flew all the way to Wellington to watch Ishant take 6-fer and flew all the way back before the whole McCullum-Watling-Neesham thing happened. Great. Did meet quite a few CWers though.
9. Trent Boult, 6/32 vs England, 2017/18
This was a genuinely glorious Test on a whole number of levels. Sitting with a mate Broad-facing as England got completely routed for 58 on the first morning (****ing lol) courtesy of Boulteh. Watching the cricketing gods extract their revenge on Joe Root for batting like a ****ing coward at the end of Day 4 as he got out to the last ball of the day, and the crowd exploding. Somehow getting into the press box and chatting to journos. Watching James Vince and Liam Livingstone in the nets and realising that England's been picking the wrong one. Witnessing Wagnerball and Tastle's puppy dog body language - "please let me have an over Kane".
10. Jack Leach, 5/32 vs Essex, 2019
Yeah sure it rained for most of the match and Somerset couldn't get the win, but fmd it was through no lack of effort from Leach and co. He was absolutely outstanding on an extremely friendly surface and comfortably out-bowled Harmer. The atmosphere when he came out to bowl in the second innings after the forfeiture and the supporters dared to half-believe was genuinely incredible. He came across as genuine and down-to-earth - as one of the supporters I was chatting to said, he's still the bloke who used to serve them at the Sainsbury's across the road. It's a shame Tresco couldn't get that first title, but I really hope Leach does.
11. Sam Cook, 4/26 vs Somerset, 2019
Cook's opening spell in the match showed some incredible potential. He got both openers early with great control and some movement (and some pretty mediocre shot selection tbf), but was near-impossible to score off and built pressure exceptionally well. Bowled a length that was simultaneously threatening and economical while Jamie Porter's usual tactic of bowling half-volleys until someone nicks one didn't pay off at all. Easily the pick of the Essex bowlers in that match. I hope he goes far.
12th Man: Matthew Nicholson, 25 vs Queensland, 2003/04
Went wicketless and was expensive in a loss, but he hit the ING sign so good for him.